To solve this, you must set up a system of equations. The first sentence says that there are two numbers and that their sum is 91, so your first equation is . For the next equation, it says that the difference of those same numbers is 1, which means that the equation is . Now, putting those two together for the system of equations, it's easiest to add them. The result will be which when simplified gives you the value of x. Taking the value of x, you can substitute in the second equation to find the value of y.
