If 7x - 5y = 20 and 12x + 5y = 75, what is the value of xy?
7x - 5y = 20 ---(1)
12x + 5y = 75 ---(2)
Eq(1) +Â (2),
19x =95
x = 5
From eq(1),
7$$\times$$5 - 5y = 20
5y = 15
y = 3
xy = 5 $$\times$$ 3 = 15
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