if y=4x then you will substitute 4x in for y in the second equation.
8x + 4x = 18 combine like terms
12x = 18 divide by 12 on both sides
x = 18/12 or 3/2
now replace x in the first equation with 3/2 to get
y = 4 3/2
y = 6
the answer is a
(3/2,6)
hope that .
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