Question 762984
Let first number be 4*x
Then the second number is 5*x

Increase the first number by 20%, it becomes 4*1.2*x = 4.8*x 
(increasing by 20% means the number increases by 0.2 - hence becomes 1.2 times the original value)

Similarly, decreasing the second number by 20%, it becomes 0.8 times the original value or 5*x*0.8 = 4*x

Hence the new ratio is 4.8*x : 4*x = {{{highlight(6:5)}}}

:)