Box of markers = $ B
Shoulder bag = Twice as much as the box of markers = $ 2B
Pen = Six less than the shoulder bag = $ (2B - 6)
Hence, the cost of pen is $ (2B - 6).
Simple....
3x-10(x+2)=13-7x
Just solve for x.....
3x-10x-20=13-7x
-7x-20=13-7x
+7x +7x
-20=13
NO SOLUTION.
Thus, your answer.
1 is for circle
2 is for triangle
3 is for surface area
4 is for volume