What is the value of r?
3/5 (r−7) =1

Solve for r by simplifying both sides of the equation, then isolating the variable.
r = 26/3

You have to do (3/5) times and then (3/5) times 7  so now u should have    3/5r - 4.2=1    now do   1+4.2 which gives u 3/5r=5.2    then divide 5.2 by 3/5 which will give you 8.666666667