82.15 / 31 = 2.65 per gallon
f + 6 = ?
Well, the answer can be pretty much any number. It all depends on what number f is. f is a variable, so you can plug in any number to replace f.
For example, if f was 5, this is what the equation would look like:
5 + 6 = 11
If f was -3, this is what the equation would look like:
-3 + 6 = 3
So, again, the answer can be anything. It depends on what f is.
Answer:
x=8
Step-by-step explanation:
5.5 + 2.1x + 3.8x - 4.1
5.5-4.1 +x(2.1+3.8)
1.4 +x(5.9)
5.9x+1.4
these are equivalent if there is a plus sign between 1.4 5.9x
We have,

Introduce variable
such that 
The sum
is therefore 
So,
(sadia's age)
(father's age)
Hope this helps :)