All you have to do is multiply length x width x height
9.71 x 2.74 x 4.23 = 112.54 
Take the amount 14 MPG (miles per gallon)
Then take the number of miles to go (133 miles to go)
Divide, like so:
133/14
= 9.5
let
x-------> walnuts that Mario eats in a week
y-------> walnuts that Yolanda eats in a week
we know that
x=2y-------> equation 1
y=6*7-------> y=42 walnuts
substitute the value of y in equation 1
so
x=2*42-----> x=84 walnuts
therefore
the answer is
Mario eat in a week 84 walnuts