Math
posted by Sarah .
Use linear combinations to solve the system of linear equations.
5x=4y30
2x+3y+12

5x = 4y  30
2x + 3y +12
(1) 5x  4y = 30
(2) 2x + 3y = 12
multiply (1) by 3(5x  4y = 30)
(1) 15x + 12y = 90
multiply (2) by 4(2x + 3y = 12)
(2) 8x + 12y = 48
ADD two new equations
(1) 15x + 12y = 90
(2) 8x + 12y = 48
23x + 0 = 42
23x = 42
x = 42/23
substitute x = 42/23 in 2x + 3y = 12
to find y
(2) 2x + 3y = 12
2(42/23) + 3y = 12
84/23 + 3y = 12
3y = 12 + 84/23
3y = 276/23 + 84/23
3y = 360/23
y = 360/23 * 1/3
y = 360/69
y = 120/23
x = 42/23,
y = 120/23