X−1.2=3 i dont understand this stupid math problem

Hi my sisters and brothers can tell me the answer because i don’t understand the question

Find an equation for the linear function which has slope -10 and x-intercept -7

Acollection of coins has value of 64 cents. there are two more nickels than dimes and three times as many pennies as dimes in this collection. how many of each kind of coin are in the collection?