I'm not sure about the answer, but this is how I would do it, since 15% and $150 are the same based on the question. do let me know if it's right! :)
Answer:
-4
Step-by-step explanation:
f(x) = 10 - 2x,
Let x= 7
f(7) = 10 2(7)
= 10-14
= -4
Answer:
1.60 
Step-by-step explanation:
Assuming that this is a cylindrical pipe, the area can be determined by applying the formula for calculating the area of a circle.
i.e Area = 

So that,
for the inner part of the pipe,
r = 
= 
= 2.5 feet
Area of the inner part of the pipe = 

= 3.14 x 
= 19.625
Are of the inner part of the pipe is 19.63
.
Total diameter of the pipe = 5 + 0.2
= 5.2 feet
r = 
= 2.6 feet
Area of the pipe = 

= 3.14 x 
= 21.2264
Area of the pipe is 21.23
.
Thus the cross sectional area = Area of the pipe - Area of the inner part of the pipe
= 21.2264 - 19.625
= 1.6014
The cross sectional area of the cement pipe is 1.60
.
Laila=l
Tom=t
Dan=d
l=t+14
l=d-5
l+t+d=51
In terms of l:
d=l+5
t=l-14
So:
l+l+5+l-14=51
3l+5-14=51
3l-9=51
3l=60
l=20
d=25
t=6
Hope this helps :)