Answer :
PEMDAS
-parenthesis
-exponents
-multiply
-divide
-add
-subtract
2+(-1)x9
2-9
-7
-parenthesis
-exponents
-multiply
-divide
-add
-subtract
2+(-1)x9
2-9
-7
Following PEMDAS, first you solve inside the parentheses;
2 + (3 - 4) * 9
2 + ( -1 ) * 9
Next, multiply;
2 + -1 * 9
2 - 9
And finally, add;
-7
2 + (3 - 4) * 9
2 + ( -1 ) * 9
Next, multiply;
2 + -1 * 9
2 - 9
And finally, add;
-7