Answer:

Step-by-step explanation:
Given



Find the length of HG
First, it should be noted that the displayed figure is a trapezium
<em>The area of a trapezium is calculated by multiplying the sum of parallel sides by half its height;</em>
In this case;

Substitute the values of Area, HE and EF


Divide both sides by 4


Subtract 12 from both sides



<em>Hence, the length of HG is 5mm</em>