Lawrence buys his friends candy in the morning for $5 a box, but forgot some of his friends, so he went back to the candy shop and purchased the same...

Lawrence buys his friends candy in the morning for $5 a box, but forgot some of his friends, so he went back to the candy shop and purchased the same candy but they had increased in price. He paid $7 a box. Let t represent the number of boxes of candy Lawrence purchased.

Write an expression that represents these purchases.