Formula for a rhombus is simply the diagonals over 2.
(The diagonals here are 12 and 15)
You could also do this intuitively. Because there is an inscribed right angle, each of the triangles inside are BH/2. Thus, the area of all four is 2BH. The base and height of each of the triangles is 6 and 7.5, so the area is 6 * 7.5 * 2.
we know that 20% of the total is peters - and peter has 12 dollars. We know that 20% 5 times gets us to 100%. So we multiply 12 by 5 to get a total answer of 60$
