Recall that

where
is the angle between the vectors
whose magnitudes are
, respectively.
We have


Cos is the adjacent (side next to the angle in question) divided by the hypotenuse (sloped side)
for angle K, this is therefore 7/25
Answer:
80 gal
Step-by-step explanation:
20 gal takes her 400 mi
Vol. of gas = 1600 ×20/400
Vol. of gas = 1600 ×1/20
Vol. of gas = 80 gal
Betty will use 80 gal of gas.