Answer:
[tex]\boxed{b=14cm}[/tex]
Step-by-step explanation:
Altitude is a perpendicular line segment from a vertex of a triangle to the opposite side. This altitude is shown in the figure and is h = 21 cm. So we need to find b, that is the base of the triangle. From the formula:
[tex]A=\frac{bh}{2}[/tex]
We can isolate b as follows:
[tex]A=\frac{bh}{2} \\ \\ b=\frac{2A}{h} \\ \\ Substituting \ values: \\ \\ b=\frac{2(147)}{21} \\ \\ \therefore \boxed{b=14cm}[/tex]
