Question 39399
Let x be one of the numbers and y the other number.

x + y = 125 The sum of the two numbers is 125.
x - y = 15 Their difference is 15.  Rewrite this as: x = y+15, substitute for x in the first equation and solve for y.
(y+15) + y = 125 Simplify and solve for y.
2y + 15 = 125 Subtract 15 from both sides.
2y = 110 Divide both sides by 2.
y = 55
x = y+15
x = 55+15
y = 70

The larger of the two numbers is 70.