One number is 5 more than twice the other number. if the sum of the two numbers is 35, find the two numbers.

Let n = unknown number
Let 2n + 5 = other number

n + 2n + 5 = 35
3n + 5 = 35
3n = 35 - 5
3n = 30
Divide both sides by 3 to isolate the variable
n = 10

Your first number, n, is 10. 
Your second number, 2n + 5, is 25.