Why is -9an acceptable answer to the equation x2=81 ?

Step-by-step explanation:

Because square of a negative number gives a positive number, that's why - 9 is an acceptable answer to the equation

139

Step-by-step explanation:

in this case, the sum of facing angles is 180°

∠ROP + ∠PQR = 180°

(x + 17)° + (6x - 5)° = 180°

7x + 12 = 180

7x = 180 - 12

7x = 168

x = 168/7 = 24°

so ∠PQR = 6x - 5 = 6(24) - 5 = 139°