Question 529648
Sure.
Suppose you have 2 equations with 
2 unknowns. It definitely should be
solvable, and one way is by substitution.
Say the equations are
(1) {{{ x - y = 10 }}}
(2) {{{ 3x^2 + 9y^2 = 300 }}}
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From(1), I get
(1) {{{ x = y + 10 }}}
Now I will Substitute this value of {{{x}}}
into equation (2)
(2) {{{ 3*( y + 10 )^2 + 9y^2 = 300 }}}
(2) {{{ 3*( y^2 + 20y + 100) + 9y^2 = 300 }}}
(2) {{{ 3y^2 + 60y + 300 + 9y^2 = 300 }}}
(2) {{{ 12y^2 + 60y = 0 }}}
(2) {{{ 12y*(y + 5) = 0 }}}
{{{ y = 0 }}}
{{{ y = -5 }}}
The solutions are
(10,0) and (5,-5)