Key by key on calculator how would I solve for x in 0205x142

Key by key on calculator how would I solve for x in 0.2=(0.5)^(x/14.2)? -Original question that brought me to that point-\"The half-reaction of 32P is 14.2 days. How many days would be required for a sample of radiopharmaceutical containing 32P to decrease to 20% of its initial activity?

Solution

x =

(ln 0.2/ln 0.5)* 14.2