What is XX plus XXIX times LI?

To solve this expression, we need to follow the order of operations, which is parentheses, exponents, multiplication and division (from left to right), and addition and subtraction (from left to right). In this case, we first need to multiply XXIX (29) by LI (51) to get 29 * 51 = 1479. Then, we add XX (20) to this result to get 1479 + 20 = 1499. Therefore, XX plus XXIX times LI equals 1499.