Answer:
In a tape diagram, each of the lengths represents a fixed quantity of something.
Let's suppose that each one of these lengths represents a distance d.
We also know that the expert trail is 750 meters longer than the beginner one.
And in the tape diagram, the expert trail has 3 more lengths than the beginner trail, then we must have that the difference in distance must be equivalent with the difference in lengths.
750m = 3*d
d = 750m/3 = 250m
Then each length in the tape diagram represents 250m
With this we can find the length of each trail.
The beginner trail has 1 length, then it is 1*250m = 250 meters long.
The expert trail has 4 lengths, then it is 4*250m = 1000 meters long.