Answer:
Rosie is 10 years old
Explanation:
A)
Rosie is x years old
Rosie's age (R) = x
R = x
Eva is 2 years older
Eva's age (E) = x + 2
E = x + 2
Jack is twice Rosie’s age
Jack's age (J) = 2x
J = 2x
B)
R + E + J = 42
x + (x + 2) + (2x) = 42
x + x + 2 + 2x = 42
4x + 2 = 42
4x = 42 - 2
4x = 40

Rosie is 10 years old