# MATH

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X= 92]96]100]104]108
Y=23]24]25]26]27

WHAT IS THE VALUE OF Y WHEN X IS 68??

IF Y=X-19, WHAT IS THE VALUE OF X WHEN Y= 34

• MATH -

Question 1:

92 - 4 = 88; y = 22
88 - 4 = 84; y = 21
84 - 4 = 80; y = 20
80 - 4 = 76; y = 19
76 - 4 = 72; y = 18
72 - 4 = 68; y = 17

When x = 68, y = 17.

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For question 2:

IF Y = X-19, WHAT IS THE VALUE OF X WHEN Y= 34.

Replace Y with 34 and solve for x.

34 = X - 19

34 + 19 = X

53 = X

Done!

• MATH -

X= 92]96]100]104]108
differences
4, 4, 4, 4

Y=23]24]25]26]27
differences
1, 1, 1, 1

when doing this type of problem, make table of change in x and change in y.
if the ratio of change in y over change in x is constant, we have a straight line.
y = m x + b
If not, make another line, the differences of differences.
if that ratio is constant, you have a parabola.
y = a x^2 + b x + c

etc. That will usually work
Anyway, here we have y = m x + b
put in two points to solve for m and b and you have everything.
we can see from our table that m = change in y / change in x = 1/4
so
y = (1/4) x + b
put in a point (92,23)
23 = (1/4)(92) + b
b = 0 remarkable
SO
y = (1/4) x
so if x = 68, then y = 68/4 = 17