How do you explain expanded notation method for 82 times 3

Ateacher has $80 to buy workbooks. each work book cost $3. if she buys as many workbooks as possible, how much money does she have leftover? a) $2 b) $4 c) $6 d) $8

Nine more than four times a number is the same as one less than twice the number. find the number?

Secant be and cf intersect at point d inside a what is the measure of cde