Maria = x
Tom = y
Use substitution
x+y=30
2y=x
2y+y=30
3y=30
y=10
Tom is 10 years old.
x+y=30
x+10=30
x=20
Maria is 20 years old.
By definition of complement,
Pr[not P | G and T] = 1 - Pr[P | G and T]
and by definition of conditional probability,
Pr[not P | G and T] = 1 - Pr[P and G and T] / Pr[G and T]
Pr[not P | G and T] = 1 - (16/100) / (33/100)
Pr[not P | G and T] = 1 - 16/33
Pr[not P | G and T] = 17/33
Answer: 11 1/2
Step-by-step explanation: