What’s the answer? and how do I do this ?

Choice C (x+2)(x+5)

Step-by-step explanation:

Choice A: 5x-2x = 3x, not right.

Choice B: 10x+7x = 17x, not right.

Choice C: 5x+2x = 7x, right.

So the answer is choice C, the clever wouldn't waste time on calculation when you know the right answer.

But if you want to know...

Choice A: Fortunately, the coefficient for x^2 is 1 which is easy to factor

Now we see -2 and 5, you don't need to calculate, just calculate -2+5 = 3 or if you want.

[5(x)]+[-2(x)] = 5x-2x = 3x

For +10, just multiply 5 and -2 then you get -10

Choice B: Same with choice one, you can find the middle expression by,

7x+10x = 17x or in advanced way

10(x)+7(x) = 10x+7x = 17x

For the last expression, jut multiply 10 and 7, you get 70 which is not even right.

Choice C is right because 5x+2x = 7x (From 5(x)+2(x)=5x+2x=7x)

Then multiply 2 and 5 to get last expression aka 10 as you get 10