Triangles IJK and LMN are similar. Then, the proportion between their similar sides must be equal. That is:
IJ/ML = JK/MN = IK/LN
where:
IJ = x
JK = 54
IK = y
MN = 42
ML = 28
NL = 35
In order to find the value of y, you consider the equation JK/MN = IK/LN, and solve for y, just as follow
JK/MN = IK/LN replace by the values
54/42 = y/35 multiply both sides by 35
(54/42)(35) = y
45 = y
Hence, y = 45
The first thing we need to distinguish is what 1 and 3/4 means. So, 3/4 = .75, so 1 and 3/4 = 1.75
So, we need 1.75 cups of flour for one batch, since you're making three batches, you need three times as much, so
1.75 * 3
5.25 is the answer, to put it back in to fractions,
5 and 1/4 cups of flour are needed.
The line through (a,b) and (c,d) is
(c-a)(y-b) = (d-b)(x-a)
Picking the last two points,
(-2 - -6)(y - -21) = (-14 - -21)(x - -6)
4(y+21) = 7(x+6)
When x=0
4y + 84 = 42
4y = -42
y = -21/2
Answer: -21/2
We never used the first point, let's check it's on the line
4(y+21) = 7(x+2)
4(-28 + 21) = -28
7(-10 + 6) = -28, good
