Pleasee help me solving systems of equations

Astudent received the following grades last semester. find the student's semester grade point average. an a is algebra (3 credits), a b in history ( 3 credits), a in sociology ( 3 credits) a d in english ( 3credits) and a c in seminar ( 2credits). an a is worth 4 points, a b is worth 3 points a c is worth 2 points and a d is worth 1 point.

X+y=-4 x-y=2 use elimination with adding and subtraction

Find two numbers if their sum is 91 and the ratio is 6: 7?