graphing and solving inequalities

Question

natalie and her sister are filling pools with water at the same time. natalie begins with 100 gallons and will add 10 gallons each hour. her sister begins with 25 gallons and will add 25 gallons each hour. when will natalie have less water in her pool than her sister?

Answer 1

N = 100 + 10x  where N is the # gallons in Natalie's pool after x hours of filling work.

S = 25 + 25x where S is the # gallons in the sister's pool after x hours of filling work.

 

When does N < S?  Just equate the two right sides of those equations, & solve this inequality.