PLZ HELP Find the value of x that makes ΔXYZ~PQR

Tim's phone service charges $26.39 plus an additional $0.21 for each text message sent per month. if tim's phone bill was $31.64, which equation could be used to find how many text messages, x, tim sent last month?

Another type of subtraction equation is 16-b=7. explain how you would sole this equation then solve it.

Joe has some money in his bank account he deposits 45$ write an expression that represents the amount of money in joe's account