Explanation:
5a + 7+ 3(a_+5) = 70 expand left side
5a + 7 + 3a + 15 = 70 gather 'like terms'
(5a+3a) + (7+15) = 70 simplfy ....and subtract 22 from both sides
8a = 48 divide through by 8
a = 6
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