She needs 27 crates to make 7 steps. It makes more sense if you draw it out for yourself.
A20-a18=a1+19d-a1-17d=2d =281-97
so
d=92
we are given two points as
(3, 16) and (5, 10)
firstly , we will find slope
slope is m
so, we can use formula

now, we can plug points



we can plug it in y=mx+b
we get

now, we can select any one points
and find b
(3,16)
x=3 and y=16

we can find b

now, we can plug back b
and we get

so, equation is

and
...............Answer
im quite positive that the x-intercept is 1,6