The way you should approach this problem depends on where you are at in your study of mathematics.
Seeing this is multiple choice, you COULD just test out each option.
For example, if 12 is correct:
Kayla has $12. Therefore Nathan has $40 - $12 = $28.
Does 3/4 of 12 (ie 9) equal half of $28 (ie $14)? NO, so option A is not the one .... test out option B, etc.
This could be time-consuming, especially if the last option is the correct one!
A better approach (and one you'd have to use if the question was not multiple choice) is to let k be Kayla's money and n be Nathan's money and form two equations and solve simultaneously.
Can you translate "Kayla and Nathan have $40 together" into an equation involving k and n?
Can you translate "3/4 of Kayla’s money Equals half of Nathan’s money" into an equation involving k and n?
Then solve simultaneously.
Let us know how you go.
PS. What does SHL stand for?