The coordinates of rhombus abcd are a(–4, –2), b(–2, 6), c(6, 8), and d(4, 0). what is the area of the rhombus? round to the nearest whole number, if necessary.
30 square units
60 square units
102 square units
120 square units

First you calculate the distance between B and D, A and C. 
We have the distance between B and D will be:  sqrt[(x2-x1)^2+(y2-y1)^2] = 8.5
The distance between A and C will be: 14.14 
We have the area of rhombus: 1/2 * 8.5 * 14.14 = 60 square units. 

The area of a rhombus is ; p is the distance between A & C, while q is the distance between B & D. To find the distance you would use the distance formula which is . Plugging in the coordinates into the distance formula you get p= and q= . From there just plug in your answers into the area formula for a rhombus and you have your answer which is 60.