No clue .. wish I could help sorry
The number 6 could replace the gap :)
Yes, a common denominator is just the smallest multiple of all numbers in a group.
So the common denominator of 4, 8 and 12 would be 4, because 4 goes into all those numbers.
That would be-
f(t)=80t+4
How I worked that out-
f(x)=mx+b
b= the y intercept which is 4
mx= your slope, which is 80t
f(t) is your height
