The sum of two numbers is 25 and their difference is 13. Find their product.

Let us assume the numbers are a and b.
According to question,
sum of two numbers = 25
a + b = 25......................(1)
difference of two numbers = 13
a - b = 13........................(2)
add the Equation (1) and (2)
a + b+ a - b = 25 + 13
⇒ 2a = 38
⇒ a = 19
Put the value of a in equation in (1)
19 + b = 25
⇒ b = 25 - 19
⇒ b = 6
Product of the numbers = a x b
put the value of a and b,
⇒ Product of the numbers = 19 x 6
⇒ Product of the numbers = 114