A man's age (a) 10 years ago is 43. Years ago means we subtract a - 10 = 43 If the problem asks you to solve for a, we type this equation into our math engine and we get: Solve for a in the equation a - 10 = 43 Step 1: Group constants: We need to group our constants -10 and 43. To do that, we add 10 to both sides a - 10 + 10 = 43 + 10 Step 2: Cancel 10 on the left side: a = 53