PLEASE HELP FAST On Monday a group of students took a test and the average ( arithmetic mean ) score was exactly 80.4. A student who was absent on Monday took the same test on Tuesday and scored 90. The average age test score was then exactly 81. How many students took the test on Monday?
A) 14
B) 15
C) 16
D) 17
E) 18
With steps please

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

i saw this question before, dont know the asnwer srry

step-by-step explanation: