simultaneous equation, solved by substitution
7x-4y=28
2x-4y= -12
7x-4y=28, equation (1)
2x-4y= -12, equation (2)
isolate y in either one of the equations,
7x-4y=28 (1)
subtract 7x from both sides,
-4y=28-7x
^^ we will call this equation (3)
-substitute equation 3 into equation 2
2x+(28-7x)= -12
simplify
-5x+28= -12
subtract 28 from both sides
-5x = -40
divide both sides by -5
x= 8
subsitute 8 into equation 2
2(8)-4y= -12
16-4y= -12
subtract 16 from both sides,
-4y = -30
divde -4 from both sides
y=7
test on either of the original equations
7(8) - 4(7)=28
56-28=28
therefore,
x=8
y=7