28 + 53 = 81.
180 - 81 = 99.
Your missing length is 99 degrees.
( Just remember that all triangles add up to 180 degrees )
If you need more help just message me
8x+15=7
In the statement the phrase the sum of can tell you that it is going to be an addition problem. So 8x ( eight times a number) would be added to the 15, 8x+15. Since its an addition problem the part where it says ' ... is seven', you know that it will all equal 7. So the answer would be 8x+15=7.
