1.what is 10+20% ?
2.what is 10-20% ?

The question can be misunderstood

10 + 20% = 10 + 20/100 = 10 + 0.2 = 10.2

But if the question is what is 10 increased by 20% it is

10 * (1 + 20%) = 10 * (1 + 0.2) = 10 * 1.2 = 12

So that is different.

Else with the other question

10 - 20% = 10 - 20/100 = 10 - 0.2 = 9.8

10 * (1 - 20%) = 10 * (1 - 0.2) = 10 * 0.8 = 8

10 - 20% = 10 - 20/100 = 10 - 0.2 = 9.8

10 * (1 - 20%) = 10 * (1 - 0.2) = 10 * 0.8 = 8

Step-by-step explanation:

x² + 3x + 7 = 0       [ax² + bx + c]

a = 1

b = 3

c = 7

quadratic formula:

    (+/- is this ±)

plug in the numbers into the variables

your answer is a