ANSWER:
The area is 145.8 mm^2
STEP-BY-STEP EXPLANATION:
We can calculate the value of the area of the green triangle by means of the following proportion:
[tex]\begin{gathered} \frac{10}{25}=\frac{18}{x} \\ \text{solving for x} \\ x=\frac{18\cdot25}{10} \\ x=45 \end{gathered}[/tex]But we must bear in mind that in the case of the proportion of areas, the area increases in proportion to the scale factor squared, therefore
[tex]\begin{gathered} fs=\frac{18}{10}=1.8 \\ \text{now, } \\ 1.8^2=3.24 \\ \text{then} \\ x=45\cdot3.24 \\ x=145.8 \end{gathered}[/tex]