Cost of home is 125900, rate of down payment is 15%, what is the down payment, and the mortgage

While scuba diving, rajeev dove to a depth of 12.6 feet below the surface of the water and then descended another 8.7 feet. what expression can be used to find rajeev's new position? 12.6 – 8.7 –12.6 – 8.7 –12.6 – (–8.7) 12.6 – (–8.7)

Evaluate the expression for the given value of the variable 7a - 4a for a =8

Math it's appreciated. (picture provided)