If $5\mathrm{a}+5\mathrm{b}+20\mathrm{c}=\mathrm{t},$ then the value of t for which the line $\mathrm{ax}+\mathrm{by}+\mathrm{c}-1=0$ always passes through a fixed point is 

Equation of line $\frac{\mathrm{ax}}{\mathrm{c}-1}+\frac{\mathrm{by}}{\mathrm{c}-1}+1=0$ has two independent parameters.

$5\mathrm{a}+5\mathrm{b}+20\mathrm{c}=\mathrm{t}$

$\therefore 5\mathrm{a}+5\mathrm{b}=\mathrm{t}-20\mathrm{c}$

$\frac{5\mathrm{a}}{\mathrm{c}-1}+\frac{5\mathrm{b}}{\mathrm{c}-1}=\frac{\mathrm{t}-20\mathrm{c}}{\mathrm{c}-1}$

R.H.S is independent of c if $\mathrm{t}=20.$