Don't know how to solve

x=12

Step-by-step explanation:

Knowing that everything is given adds up to 90º(because the angle is a right angle), we can easily solve for x.

(x+42)+3x=90

Gather like terms.

4x+42=90

Subtract 42 from both sides of the equation.

4x=48

Divide 4 from both sides of the equation.

x=12

Hope this helps :)

the diameter is 16 cm. are you a teacher?

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