If a = 7, what is a − 2(a − 1)?

If a = 7, what is a − 2(a − 1)?

• A. -1
• B. 5
• C. -5
• D. 7

Answer: (C)

Evaluating expressions by substituting a value and simplifying using the distributive property is what's being tested. Replace a with 7: 7 − 2(7 − 1). Inside the parentheses, 7 − 1 = 6, then 2 × 6 = 12, and 7 − 12 = -5. Another way is to distribute first: a − 2(a − 1) = a − 2a + 2 = -a + 2; with a = 7, that gives -7 + 2 = -5. So the value is -5.

Evaluating expressions by substituting a value and simplifying using the distributive property is what's being tested. Replace a with 7: 7 − 2(7 − 1). Inside the parentheses, 7 − 1 = 6, then 2 × 6 = 12, and 7 − 12 = -5. Another way is to distribute first: a − 2(a − 1) = a − 2a + 2 = -a + 2; with a = 7, that gives -7 + 2 = -5. So the value is -5.