Question

I need to solve this algebra expression

Answer 1

Ok so they subtract instead of add because if you said I could have $5 to spend at the mall for an example and I took 7  I would have to pay you back. But what happens if you take 5 away from seven is you would get -2 so you would subtract that 2x10. You subtract it because it's a negative number. Does that make sense?

Answer 2

$5-7+2*10$
$5-7+20$
$-2+20=18$
The answer is :18