Use the percent proportion to solve each problem 25 is 80% of what number

31.25

Step-by-step explanation:

a is the unknown number

80% of a=25

80/100 x a=25

80a/100=25

Cross multiplying we get

80a=25 x 100

80a=2500

Divide both sides by 80

80a/80=2500/80

a=31.25

step-by-step explanation:

abc

x = ±sqrt(10)

step-by-step explanation:

5 - 2x² = -15

subtract 5 from each side

5-5 - 2x² = -15-5

-2x^2   = -20

divide by -2 on each side

-2x^2   /-2= -20/-2

x^2 =10

take the square root on each side

sqrt(x^2 )=±sqrt(10)

x = ±sqrt(10)

check:

5 - 2x² = -15

+sqrt(10)

5 - 2(sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15

-sqrt(10)

5 - 2(-sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15