The area of a triangle of height h and base b is:
[tex]A=\frac{bh}{2}[/tex]
Solving for b:
[tex]b=\frac{2A}{h}[/tex]
If the height is 15 and the area is 75:
[tex]b=\frac{2(75)}{15}=10[/tex]
The area of a triangle of base b = 10 and height h = 12 is:
[tex]A=\frac{10\cdot12}{2}=60[/tex]
Answer: 60
