Answer:
b = 10 mm
Step-by-step explanation:
the area (A) of a triangle is calculated as
A = [tex]\frac{1}{2}[/tex]bh ( b is the base and h the height )
given A = 30 and h = 6 , then
[tex]\frac{1}{2}[/tex]b × 6 = 30 , that is
3b = 30 ( divide both sides by 3 )
b = 10