Step-by-step explanation:
-4x + 7y = 20 ... equation 1
y= 3x + 15 ...equation 2
Rewriting the equations:
7y - 4x = 20
y - 3x = 15
using elimination method:
I want to eliminate y. So, I multiply equation 2 by 7 so both equations can have same coefficient
7y - 4x = 20 ... equation 1
7y - 21x = 105 ...equation 2
subtract equation 1 from 2:
7y - 7y -21x - (-4x) = 105 - 20
-21x + 4x = 85
-17x = 85
divide both sides by -17:
-17x/-17 = 85/-17
x = -5
To get y, we insert the value for x in any of the equation
using equation 1
7y - 4(-5) = 20
7y + 20 = 20
7y = 20-20
7y = 0
y = 0/7
y = 0
x = -5 and y = 0