The circumference of a slowly growing tree increases by an average of 7/8 inch every 5 year how much will the tree grow in just one year

To find the growth of the circumference of the tree in one year, you create the fraction 1/5 to represent the part of the 5 years you want to calculate the circumference for.

1/5 of the 7/8 in math means
1/5 x 7/8 or 7/40 inch

The circumference of a tree will grow 7/40 of an inch each year.