Solve using substitution:
x^2+3y^2=172
2x-y=3

Question

anonymous · Answer

Get y by itself in second equation

anonymous · Answer

y = 2x-3.
use that in the first equation. you will get a quadratic in x.
solve for x and use those values of x to find y.

anonymous · Answer

y=-3-2x
substitute y in the first equation

anonymous · Answer

x^2+3(-3+2x)^2=172                                     2(11.15)-y=3                 
x^2+3(9+4x^2)=172                                       22.3-y=3
x^2+27+12x^2=172                                       -y=3-22.3
13x^2=172-27                                                -y/-1=-19.3/-1
13x^2=145                                                     y=19.3
13x^2/13=145/13
x^2=11.15384615$$\sqrt{?}$$
x=11.15