how do i solve this?

Answer:
[tex]5.4 cm^{2}[/tex]
Step-by-step explanation:
The area of triangle is given by 0.5bh where b is the base while h is height. Therefore, A=0.5bh
For triangle ABC
15=0.5*5*h
H=6cm
Using the concept of similarity and enlargement
[tex]\frac {B_a}{B_d}=\frac {H_a}{H_d}[/tex]
Where B and H represent base and height respectively. Subscripts a and d represent triangle ABC and DEF.
Therefore
[tex]\frac {5}{3}=\frac {6}{H_d}\\H_d=3.6\ cm[/tex]
Area will be
[tex]A=0.5*3*3.6=5.4\cm^{2}[/tex]