Answer:
Jo's age = x = 8 years
Step-by-step explanation:
Let
Jo's age = x
Jo's mother, Anne's age = 4x
In four years time, Anne will be three times as old as Jo.
Jo's age =3( x + 4)
Jo's mother, Anne's age = 4x + 4
How old is Jo?
Equate Jo's age and his mother's age
3(x + 4) = 4x + 4
3x + 12 = 4x + 4
3x - 4x = 4 - 12
-x = - 8
Divide both sides by -1
x = 8
Therefore,
Jo's age = x = 8 years
#7. C #10. C #11. A #12. C
In this question , we have to find, which option represents inverse functions.
Let's check out option b
Let it be y
So we have

Switching x and y and solving for y,

Performing cross multiplication

Combining like terms


Which is same as of the other function.
So correct option is b .
Ratio:
Red : Total
2 : 5
(x2) (x2)
4 : 10
Green : Total
3 : 10
Total of red and green marbles = 4 + 3 = 7
Blue marbles = 10 - 7 = 3
10 parts = 40 marbles
1 part = 40 ÷ 10 = 4
3 parts = 4 x 3 = 12
Answer: There are 12 blue marbles.