> syms a, b, c, d.
> eq1='(1 - a * b ^ 2 * 180 * 0.0001) * (2519.142-16628/c)/(2923556.1 * b ^ 2) + 2.83 * 0.001 * [[(2 * c - 3030) ^ 2.5 * 0.558 * b * c ^ 2-2503631430 * (1 + 0.03 * b)] * exp (10 * (303/c - 1))]/[91809 * c ^ 2 * (0.043 + 17.18 * 39.85 * d d d ^ ^ 2 + 36 * 3-0.0634-3 * b)] + 8 * 0.00001 * (1 - b - 2416/c) * 8.314 ^ (1 - b) * 268738.56 * 96487 ^ ^ b (b - 2)/(0.288 * (2.563-0.33 * (0.043 + 39.85 * 17.18 * d d d ^ ^ 2 + 36 * 3) + 0.0264 * (0.043 + 17.18 * 39.85 * d d d ^ ^ 2 + 36 * 3) ^ 2-0.000671 * (0.043 + 17.18 * 39.85 * d d d ^ ^ 2 + 36 * 3) ^ 3] * 10 ^ (6)]]=0'.
> eq2='(1-a*b^2*180*0.0001)*[[(-0.459)*0.001*(1+0.03*b+0.062*b^2.5*c^2/91809)*(17.18-79.7*d+108*d^2)*exp[10*(303/c-1)]-[0.33+0.0528*(0.043+17.18*d-39.85*d^2+36*d^3)-2.013*0.001*(0.043+17.18*d-39.85*d^2+36*d^3)^2]*(17.18-79.7*d+108*d^2)]/[180*0.0001*(0.043+17.18*d-39.85*d^2+36*d^3-0.0634-3*b)^2]*[665.12*c*exp[2416*(1/c-1/303)]/[2681205457*[3118808929/c]^(-b)*[2.563-0.33*(0.043+17.18*d-39.85*d^2+36*d^3)+0.0264*(0.043+17.18*d-39.85*d^2+36*d^3)^2-0.000671*(0.043+17.18*d-39.85*d^2+36*d^3)^3]^2]]=0';
> eq3='(1-a*b^2*180*0.0001)*[8.314*c*[1-ln(303*b/(5*0.01*c*exp(16628*(1/303-1/c)/8.314)))]/(9648.7*b^2)+0.459*0.001*[(0.03+0.155(c^2/91809)*i^1.5)*(0.043+17.18*d-39.85*d^2+36*d^3-0.0634-3*b)+3(1+0.03*b+0.062*c^2*b^2.5/91809)]/[180*0.0001*exp[10(1-303/c)]]+[6.6512*0.0001*c*exp(2416*(1/c-1/303))/[10^(-6)*2.68*10^13*[2.563-0.33*(0.043+17.18*d-39.85*d^2+36*d^3)+0.0264*(0.043+17.18*d-39.85*d^2+36*d^3)^2-0.000671*(0.043+17.18*d-39.85*d^2+36*d^3)^3]]]*(2.59298*(10^10)/(8.314*c))^b*ln(2.59298*(10^10)/(8.314*c))-2*a*b*180*0.0001*[8.314*c*ln(303*b/(5*0.01*c*exp(16628*(1/303-1/c)/8.314)))/(9648.7*b^2)+0.051*0.0001/(180*0.0001)*9[1+0.03*b+0.062*(c/303)^2*i^2.5*exp(10-(1-303/c))]/(0.043+17.18*d-39.85*d^2+36*d^3-0.0634-3*b)+(6.6512*0.0001*c*exp(2416*(1/c-1/303)))/[10^(-6)*2.68*10^13*[2.563-0.33*(0.043+17.18*d-39.85*d^2+36*d^3)+0.0264*(0.043+17.18*d-39.85*d^2+36*d^3)^2-0.000671*(0.043+17.18*d-39.85*d^2+36*d^3)^3)]]*(2.59298*10^10/(8.314*c))]+1.229*180*0.0001*a=0';
> eq4='b - 180 * 180 * 0.0001 * 1.229 * 0.0001 * b ^ 2 * 8.314 * * ln c (303 * b/c (5 * 0.01 * * exp (16628 * (1/303) - 1/c/8.314)))/(9648.7 * b ^ 2) + 0.0001/(180 * 0.0001 * 0.051 * 9 [1 + 0.03 + 0.062 * * b (303) c/I ^ ^ 2 * 2.5 * exp (10 -) (1-303/c)]/(0.043 + 17.18 * 39.85 * d d d ^ ^ 2 + 36 * 3-0.0634-3 * b) + (6.6512 * 0.0001 * c * exp (2416 * (1/c - 1/303)))/(10 ^ (6) * 2.68 * 10 ^ 13 * [2.563-0.33 * (0.043 + 17.18 * 39.85 * d d d ^ ^ 2 + 36 * 3) + 0.0264 * (0.043 + 17.18 * 39.85 * d d d ^ ^ 2 + 36 * 3) ^ 2-0.000671 * (0.043 + 17.18 * 39.85 * d d d ^ ^ 2 + 36 * 3) ^ 3)]] * (2.59298 * 10 ^ 10/(8.314 * c))] - 20000=0'.
> [a, b, c, d]=solve (eq1, eq2, eq3, eq4, 'a', 'b', 'c', 'd')