Here's the right way:


Here's the way they want you to do it:



Answer:
y=17/5 ,x= 38
Step-by-step explanation:
-4+5y =13 add 4 both side
4-4+5y=13+4
5y=17
5y/5=17/5 y=17/5
x-5y=21
x-5(17/5)=21
x-17=21
x=21+17= 38
Answer:
2
Step-by-step explanation:
m^2 + 5m - 4
Let m = -6
( -6) ^2 + 5(-6) -4
Exponents first
36 + 5(-6) -4
Then multiply
36 -30 -4
Then subtract
6 -4
2
A stuntman jumping off a 20-m-high building is modeled by the equation h = 20 – 5t2, where t is the time in seconds. A high-speed camera is ready to film him between 15 m and 10 m above the ground. For which interval of time should the camera film him?
Answer:

Step-by-step explanation:
Given:
A stuntman jumping off a 20-m-high building is modeled by the equation
-----------(1)
A high-speed camera is ready to making film between 15 m and 10 m above the ground
when the stuntman is 15m above the ground.
height
Put height value in equation 1





We know that the time is always positive, therefore 
when the stuntman is 10m above the ground.
height
Put height value in equation 1







Therefore ,time interval of camera film him is 