6 times the sum of a number and 3 is equal to 42. What is this number? The phrase a number means an arbitrary variable, let's call it x. The sum of a number and 3 means we add 3 to x: x + 3 6 times the sum: 6(x + 3) The word is means an equation, so we set 6(x + 3) equal to 42 to get our algebraic expression of: 6(x + 3) = 42 If the problem asks you to solve for x, then you type this equation into our search engine and you get: x = 4