You have to use soh coa toa.. the equation is set up to use sine
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.
Answer:

Step-by-step explanation:
Give me brainllest
6 - 5/2
which in turn results into 7 halfs
(7/2)
5.21 would just be 5 or 5.2 depending on what place you need to round.