How do i find the variable and leave in fraction 3 + 8/7d = -1

Terri makes a quilt using three sizes of fabric squares the side lenght of each fabric square is the square root of the area

Florence price's brownies and more sells all types of cookies and pastries. on tuesdays, they markdown all brownies 75% to a sale of $1.50 a dozen. find the selling price and the markdown of a dozen brownies.

What is the result of adding the system of equations? 2x+y=4 3x-y=6