With explanation plz..

( -2) + 9 * 10

order of operation

Parentheses, Exponent, Multiply, Division, Addition, Subtraction is your order (aka PEMDAS). Multiply 9x10 which gives you 90, then add -2 (or subtract 2) and your answer is 88.

Remember PEMDAS.
Parenthesis
Exponent
Multiplication/Division
Addition/Subtraction
First you see if there is anything that needs to be solved in perentheses. Insidently there is not. The only thing that is in perentheses is an integer and not an equation. Then you see if there is any exponents, yet again there is not. Next you find any Multiplication or Division. These go together and are solved from left to right in this equation there is a multiplication. Finally you solve the additon and subtraction together. There is an instance of this as well. Here is how to work it out.
(-2) + 9 * 10
= (-2) + 90
= 90 - 2
= 88
((-2) + 90 is the same thing as 90 - 2 so you can write it that way if it is easier for you)

Hope this helps!!!

A: 18/15b : 7 - -8 = 15 , 12 - -6 = 18 the y variable always goes over the x variables, c : same thing a