In 10 years Linda will be as old as Bobby is now...

[AAPL]

In 10 years Linda will be as old as Bobby is now. Thirty years ago Bobby was twice Linda's age. How old is Linda now?

A. 20
B. 30
C. 40
D. 50
E. 60

The OA is C.

I don't have clear this PS question, but I think that I can solve it of the following way,

I have this equation B=L+10, where B, is Bobby's age and L is Linda's age.

Then I have 2*L=B-30.

I have an equations system of 2 equations with 2 incognits, right?

I appreciate if any expert explain it for me. Thank you so much.

[GMATWisdom]

In 10 years Linda will be as old as Bobby is now. Thirty years ago Bobby was twice Linda's age. How old is Linda now?

A. 20
B. 30
C. 40
D. 50
E. 60

The OA is C.

I don't have clear this PS question, but I think that I can solve it of the following way,

I have this equation B=L+10, where B, is Bobby's age and L is Linda's age.

Then I have 2*L=B-30.

I have an equations system of 2 equations with 2 incognits, right?

I appreciate if any expert explain it for me. Thank you so much.

Sir your first equation B= L+10 is ok assuming Lindas and Bobbys present age as L and B
but your second equation is wrong because 30 years ago Lindas age would be L-30.
So the correct equation would be 2*(L-30)= B-30.
Putting B=L+10 in the equation we get 2*(L-30) =L+10 -30
Solving this we get L=40
Hence option C is correct

[Scott@TargetTestPrep]

In 10 years Linda will be as old as Bobby is now. Thirty years ago Bobby was twice Linda's age. How old is Linda now?

A. 20
B. 30
C. 40
D. 50
E. 60

We can let B = Bobby's current age and L = Linda's current age; thus:

L + 10 = B

and

(L - 30) * 2 = (B - 30)

2L - 60 = B - 30

2L - 30 = B

Substituting, we have:

2L - 30 = L + 10

L = 40

Answer: C