For this problem, we will simply use the distributive property both forwards to gather all of the like terms, and then backward to simplify the like terms.
5 ( a + 6 ) - a + 7a - 18
= 5a + 30 - a + 7a - 18
= 5a - a + 7a + 30 - 18
= a ( 5 + -1 + 7 ) + 30 - 18
= a ( 4 + 7 ) + 12
= a ( 11 ) + 12
= 11a + 12
Hence, the simplification for 5(a+6)-a+7a-18 is 11a + 12.
