Question

solve equations by elimination method
5x+7y=31
4x-y=5

Answer 1

Eq 1 : 5x + 7y = 31
Eq 2 : 4x - y = 5

multiply Eq 1 by 4 and Eq 2 by 5
(5x+7y=31)4 = 20x+28y=124
(4x-y=5)5 = 20x-5y=25

subtract Eq 2 by Eq 1
20x+28y=124
20x-5y=25
(-)  (+)   (-)
___________
0 + 33y = 99
____________

33y=99
y=99/33
y=3

Substitute the value of y in Eq 1
5x+7y=31
5x+7(3)=31
5x+21=31
5x=31-21
5x=10
x=5/10
x=2