Hey there!
So the "x" in the equation represents a number that is multiplied by 2 and subtracted by the number 3.25 and is equivalent to 7.15 . . . .
Multiply the numbers 2 and 5.2 . . .
2 x 5.2 = 10.4
2 x 5 = 10
2 x .2 = .4
= 10.4
Now, subtract the numbers 10.4 and 3.25 . . .
10.4 - 3.25 = 7.15
x = 5.2
The number 5.2 is correct, and the steps above is the reason as to why it is correct. :)
Hope this helps you.
Have a great day!