now, we're assuming she made the deposit at the child's birth, namely when year was 0, at the child's twenty-first birthday that'll be 21 years later.

Multiply 84 times 2 to find it hopes this helps.
3 probably it makes the most sense if you ask me
For the functions f(x) = 4x + 7 and g(x) = -9x + 11, find f(g(0)). For the functions f(x) = 3x2 - 7 and g(x) = -3x2 + 4, find f(g(2)). (Do NOT put commas in large numbers.)