What is the solution of the system ? Use substitution y=2x+7 y=x-1

What is the smallest integer n such that n\sqrt{2} is greater than 20

You are a clerk at convenience store. a customer owes 11.69 for a bag of potatoes chips. she gives you a five dollar bill. how much change should the customer receive?

Liz had 140 pens and inna had 100 pens. after inna gave liz some pens, liz had 3 times as many pens as inna. how many pens did inna give liz?