Can anyone me i don’t understand plz

It's a composite function, which means you need to apply the function to 'g' first, and once you've worked out the result, apply it to 'h'. You work from the inside out.

Therefore, g(t) = 3(t+1), so g(-6) = 3(-6+1)
-6 + 1 is -5, and 3 times -5 is -15. So g(-6) is equal to -15.

Now we apply -15 to the h function, which is h(t) = 2t. So h(-15) = 2(-15). The answer to that is -30.

Hence, your final answer is -30.