Divide both sides by 4/5 or multiply by the reciprocal.
Flip 4/5 to get the reciprocal.
The reciprocal of 4/5 is 5/4 so we will multiply both sides by that.
5/4 8/9 = 4/5 5/4 k
4/5 and 5/4 cancel out so now you have
5/4 8/9 = k
multiply top and bottom
(5 8 )/(49)
40/36
Simplify
10/9