Everything you need to do is to follow the orders of operations: Parenthesis, multiplication and division, and at last addition and subtraction.
7+(8-4)*10
First let's get ride of the parenthesis (8-4):
(8-4) = 4
So 7 + (8-4) * 10 = 7 + 4 * 10
Then, you calculate everything that is related to a multiplication or a division. In this equation, we only have 1 multiplication (4*10) but no divisions.
4*10 = 40
So 7 + 4 * 10 = 7 + 40
And now you calculate this addition:
7 + 40 = 47.
So 7+(8-4)*10 = 47 (Answer D)
Hope this Helps! :)