How can you subtract integers in real-world situations ?

Can someone check if i did this correct. it’s number 4 if you’re wondering.

If you double the input of a function and it results in half the output, and if you triple the input and it results in a third of the output, what can be guessed about the function? check all that apply.

In δabc, m∠acb = 90°, cd ⊥ ab and m∠acd = 45°. find: a find cd, if bc = 3 in