Answer:
SOH CAH TOA
Little triangle first - hypotenuse is 4, now we used this info help us find the opposite.
Opposite & Hypotenuse - Sin
Sin(45) = O/H
Sin(45) = O/4
x 4 both sides, to get Opposite
Opposite = 4 x Sin(45)
= 2 root 2
= 2.8284.......
Big Triangle next,
Opposite is 2.8284......
Y is the adjacent
Opposite & Adjacent - Tan
Tan (30) = O/A
Tan(30) = 2.8/A
x A
A x Tan(30) = 2.8
÷Tan(30)
A = 2.8 ÷ Tan(30)
A= 2 root 6
A= 4.8989...
So, y is 5 to 1 significant figure
Or
Y = 4.9 to 1d.p
(Haven't rounded anything in my calculation, even though it's shown that way, in my workings. So, you can follow along)
Hope this helps!