Answer:
x = 81.99
Explanation:
x + 7y = 64
7y = 64 - x (1)
x + 3y = 28
3y = 28 - x (2)
From equation (1) and (2)
7y = 64 - x
3y = 28 - x
Substituting 7y by 64 - x in equation (2)
3(64 - x) = 28 - x
192 - 3x = 28 - x
Adding x to both sides
192 - 2x = 28
Subtracting 28 from both sides
164 - 2x = 0
Divide both sides by 2
82 - x = 0
Adding x to both sides
82 = x
Substituting x by 82 in equation (1)
7y = 64 - 82
7y = -18
Divide both sides by 7
y = -18/7
y = -2.57
Substituting y by -2.57 in equation (1)
x + 7(-2.57) = 64
x - 17.99 = 64
Adding 17.99 to both sides
x = 81.99