The triangles are similar.
Find the lengths x and y.

X = 10.8 cm
y = 7.6 cm
This is because shapes classified as similar are proportional meaning you need to find the scale factor to find the missing values. To do so you can take corresponding vales from the each triangle and divide;
16.8 / 5.6 = 3
This means the scale factor is 3 for the small to large triangle and 1/3 for the large to small.
So;
3.6 (3) = 10.8cm
22.8 (1/3) or 22.8 / 3 = 7.6cm