So the proportions are respectively:
16:80
7:35
for long and deep. Therefore the dimensions are equivalent because there is a ratio of 5 between the dimensions:
16(5) = 80
7(5) = 35
Parallel lines will have the same slope.
so if one of the lines has a slope of 1.3, then its parallel line will also have a slope of 1.3
Find the unit rate:
1/4 yd 1(5)
---------- = -------- = 5/4 yards, or 1 1/4 yards, in one hour. This is 1.25 yards.
1/5 hr 4(1)
to find the point, find the location
realize that the shortest line that crosses through the origin and y=9x+8 is perpendicular to y=9x+8
perpendicular lines have slopes that multiply to get -1
y=9x+8 has a slope of 9
9*m=-1, m=-1/9
the slope of the mystery line is -1/9
since it passes through the origin, the y intercept is 0
y=(-1/9)x is the equation of the line from the point to the origin
find the intersection of this line and the original line
set them equal to each other
(-1/9)x=9x+8
multily both sides by 9
-x=81x+72
minus 81 both sides
-82x=72
divide both sides by -82
x=-36/41
find y
y=(-1/9)x
y=(-1/9)(-36/41)
y=4/41
the point is 
We have to add the amounts:
4(2x+3y) + 3(5x+4)
First, though, we have to distribute:
4*2x + 4*3y + 3*5x + 3*4
8x + 12y + 15x + 12
Now we just need to simplify:
23x + 12y + 12
The students planted 23x + 12y + 12 trees total.