64 is 4 times the difference between Sarah's age, a, and 44. Assume Sarah is older than 44.

64 is 4 times the difference between Sarah's age, a, and 44. Assume Sarah is older than 44.

The phrase difference between means we subtract 44 from a:
a - 44

The phrase 64 is means an equation, so we set a - 44 equal to 64
a - 44 = 64 <-- This is our algebraic expression

If you want to solve for a, then we type this expression into our search engine and get:
a = 108