Solving ya Systems of Equations by elimination

Question

-14x+15y=3

21x-20y=-10

The LCM is 42 so I am able to get

(-14x +15y=15)3 = -42x+45=45
(21x-20y=-10)2 = 42x-40y=-20
y =7
but when I plug it in to try and figure out x I do not get a whole number, can you help?

Answer 1

well, I am inclined to multiply first equation by 4 and second by 3

-56 x + 60 y = 12
+63 x - 60 y + 30
------------------- add
7 x = 42
so
x = 42/7
then
-14(42/7) + 15 y = 3
-84 + 15 y = 3
15 y = 87
y = 87/15
=========================
try that in the second one to check
21(42/7) -20(87/15) = ?
126 - 116 = 10 sure enough