What is the lower bound for 9.87 rounded to the nearest two decimal places?

Solve the problem by making up an equation. a child is 12 years old, and his father is 32 years older. in how many years will the age of the father be 3 times the age of the child?

Solve for n? [tex]z = \frac{3}{4} mn[/tex]

Ijust need these 2 questions answered (the second pic is just confirmation i'm not confident in that answer)