10x - 6y = 34 ----------------(1)
y= -5x + 21 ------------------------(2)
substitute y= -5x + 21 in equation (1)
10x - 6(-5x + 21) = 34
open the parenthesis
10x + 30x - 126 = 34
40x - 126 = 34
add 126 to both-side of the equation
40x - 126 + 126 = 34 + 126
40x = 160
Divide both-side of the equation by 40
x= 4
substitute x=4 into equation (2)
y = -5(4) + 21
y = -20 + 21
y = 1
The solution is
(4, 1)