What is the missing value in the equation
2 3/12+3\? =2 5/8

 2 3/12 +3/x = 2 5/8

simplify to

9x+12/4x = 21/8

Cross multiply

(9x+12)/(4x) = 21/8

(9x+12)*(8) = 21*4x

72x+96 = 84x

Subtract 84 x from both side

72x+96 - 84x = 84x -84x

-12x+96 = 0

Subtract 96 from both sides

-12x+96-96 = 0-96

-12x = -96

Divide both sides by 12

-12x/-12 = -96/-12

x = 8

The missing value is 8

answer: no

step-by-step explanation:

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