Hey guys, I need help with this question. Please show working out, thanks

Answer:
Step-by-step explanation:
In similar triangles corresponding triangles are in same ratio.
[tex]\frac{15}{5}=\frac{12}{y}[/tex]
Cross multiply,
15 * y = 12 * 5
y = [tex]\frac{12*5}{15}[/tex]
y = 4