Final answer:
The Hanson's can travel 78 miles until they are on E.
Step-by-step explanation:
To find the number of miles the Hanson's can travel until they run out of gas, we subtract the distance they have already traveled from the maximum distance they can go. Let's label the variable 'x' as the number of miles they can travel until they are on E.
We know that they have already gone 12 miles, so the equation becomes:
x = 90 - 12
Simplifying the equation, we get:
x = 78
Therefore, the Hanson's can travel 78 miles until they are on E.