Remark
The easiest way to solve this is to change the fractions into decimals.
2/5 = 0.4
9/10 = 0.9
k/4 = 1/4 k = 0.25 k
0.4 + 0.25k = 0.9 Subtract 0.4 from both sides.
0.25k = 0.9 - 0.4
0.25k = 0.5 Divide by 0.25
k = 0.5 / 0.25 Use your calculator for this if you don't know how to do it.
k = 2 <<<< answer.
