Question 159384
We know that 13 years ago Mary was 5/17 Grace's age. This is algebraically 
written as M-13=5/17G
M=Mary's age now
G=Grace's age now
J=Jim's age now
Two years from now Mary will be 1/2 of Jim's age. We write this algebraically as:
 1/2J=(M+2)

We also know that J+M+G=118

Isolate J by mutilplying both sides by to get
J=2(M+2)
Isolate G by Multiplying both sides of the equation by 17/5 to get

17/5(M-13)=G

Substitute J=2(M+2)

and G=17/5(M-13)

into 2(M+2) +17/5(M-13) +M=118

Multiply all the terms by 5 to get rid of the denominator

10(M+2)+17(M-13)+5M=590

Use the distributive property
10M+20+17M-221+5M=590

Combine like terms and simplify the equation.

(10+17+5)M-201=590

32M-201=590

Add 201 to both sides of the equation

32M=791

Divide by 32 on both sides
and get 24.7 Round up and it would be 25

Plug in to see if it makes sense.

1/2J=(M+2)

Mary would be 27 and Jim would be 54

25+54+G=118

Grace would be 39

(25-13)=5/17(39)

12=11.5 Round up would be 12.

Therefore in 5 years Mary=30 Grace=44 Jim=59