You can use the PEMDAS expression,
P in PEMDAS is = parentheses
E in PEMDAS is = Exponents
M in PEMDAS is = Multiply
D in PEMDAS is = Divide
A in PEMDAS is = Add
S in PEMDAS is = Subtract. You have to do each in order.
There are one parentheses sets in 90+(-3-)-10
Evaluate -3
Evaluate -
(-3-) = -3
Simplfying the expression, it becomes = 90-3-10
There is no Exponents in the expression. so skip E in PEMDAS
There is no Multiplying in the expression. So skip M in PEMDAS
There is no Division in the expression. So skip the d in PEMDAS
However, there is Adding and subtracting in this expression, There are 2 addition and subtraction signs in 90-3-10 Simplfying the expression by evaluating our addition and subtraction terms, it becomes: our answer is 77