Adding you make it the opposite of
3x + 4(2) = 20
3x + 8 = 20
3x = 12
x = 4
(4,2)
You have y=2 then all you need to do is plug 2 into the y in the equation 3x + 4y = 20 and do the math to find x. Hope this helps
M + e + f = 11
e = 1/5m
f = 3m
m + 1/5m + 3m = 11 <== ur equation
5/5m + 1/5m + 15/5m = 11
21/5m = 11
m = 11 / (21/5)
m = 11 * 5/21
m = 55/21
m = 2.619 rounds to 2.62...milk
e = 1/5m
e = 1/5(2.62)
e = 0.53 .....eggs
f = 3m
f = 3(2.62)
f = 7.86...fabric softener