r^8=5

If the problem is "r divided by 8 = 5", then  r/8 = 5     --->     multiply both sides by 8     --->     5x8  =  40.

 

If the problem is "r^8  = 5", then  r⁸ = 5     --->     take the 8^th root of both sides     --->     5^1/8  =  1.222844...