Step-by-step explanation:
Given
Find the length of HG
First, it should be noted that the displayed figure is a trapezium
The area of a trapezium is calculated by multiplying the sum of parallel sides by half its height;
In this case;
Substitute the values of Area, HE and EF
Divide both sides by 4
Subtract 12 from both sides
Hence, the length of HG is 5mm