You have to use PEMDAS (Parentheses Exponents Multiplication/Division Addition/Subtraction) to solve this,
Because you don't have any parenthesis or exponents you start with Multiplication/Division. This means you do 4*3 to get 26+5-12
Then, you move to Addition/Subtraction in which you complete left to right, So you do 26+5 to get 31-12
Finally you subtract 31-12 to get 19
Find the volume of the large box:
15x25x29
375x29
10,875cm³
and the smaller box:
10x10x10
100x10
1,000
then subtract
10,875-1,000=9,875cm³ remaining
