Do what is in brackets first, then the multiplication.
Answer:
10=10
Step-by-step explanation:
y-3x+15=10
y=3x-15+10
y=3x-5
subtitute y=3x-5 in the above equation:
3x-5-3x+15=10 (3x will be eliminated with -3x)
-5+15=10
10=10
(i hope this is the way you want the answer but at least I think it is correct)

Sounds like that to me but that is symbolically showing of that's what your teacher means as mathematical sentence
Answer:
f(g(2)) = 102
Step-by-step explanation:
f(x) and f(g(2))
As we can see, we can find g(2) and substitute this value into
f(x)=x² + 2x + 3 instead of x.
g(x) = x² + 5, g(2) = 2² + 5 = 9
f(x)=x² + 2x + 3
f(9)=9² + 2*9 + 3= 102
Answer:
#2 is a ratio so you gotta add.
#3 it’s just adding it for example 2p + 5a = 7pa