Can you guys help me with this ?

Mat bought a phone for $100. he has to pay $30 per mouth. if he has paid $640 in total, how many mouth has he had the phone?

Gabrielle's age is two times mikhail's age. the sum of their ages is 84. what is mikhail's age?

Anne plans to increase the prices of all the items in her store by 5%. to the nearest cent, how much will an artist save if the artist buys a canvas and a frame that each measure 24 by 36 inches before the price increase goes into effect?