How to find the area of rectangles, triangles, parallelograms, trapezoids

Which statement justifies why angle ebc measures 90?

Kayla and alberto are selling fruit for a school fundraiser. customers can buy small boxes of grapefruit and large boxes of grapefruit. kayla sold 3 small boxes of grapefruit and 1 large box of grapefruit for a total of $65. alberto sold 1 small box of grapefruit and 1 large box of grapefruit for a total of $55. what is the cost each of one small box of grapefruit and one large box of grapefruit?

Solve for b. ab + c= d b= a + old ob=allc-ch b= (d-c/a