Can someone help me and explain what to do here?

What is the length of the midsegment of a trapezoid with bases of length 15 and 25 ?

The unpaid balance on a mastercard charge was $1,056.23. during the month, payments of $300 and $250 were made and charges of $425 and $274.16 were added. if the finance charge is 1.2% per month on the unpaid balance, find the new balance at the end of the month. $1,205.39 $1,218.06 $918.06 $1,768.06

Of . 3x+4y+4z=4, 5x+7y+3z=5 4x+5y+7z=7