Heterogenous mixtures are unevenly mixed. Like oil and vinegar in vinaigrette if it is not emulsified well enough and they separate. Any case where two things are not evenly distributed within each other.
Homogenous mixtures are evenly mixed throughout. Like salt water or kool-aid (when it's mixed).
Hope this helps!
She needs to know the distance from LA to SF.
Call that distance x. Then you can calculate the cost from:
# of gallons consumed: x miles / 38 miles/ gallon = (x/38) gallons
After that,
cost = # gallons * cost per gallon = (x/38) gallons * 4 $/gallon = 4x/38 $
The last row going across