Hey <parent603>

Following is my worked solution (with brief explanation):

<After>

After K gave 1/7 of his share to L, K left with 6 parts. Hence, the model becomes ...

K: |----|----|----|----|----|----|

L: |----|----|----|----|----|----|10|

<Before>

Apply <work backward> method, K would have that 1 part {K did not give 1/7 of his share to L} while L would not have that 1 part. Given that L's share was $90 less than K, the model becomes ...

K: |----|----|----|----|----|----|----|

L: |----|----|----|----|----|10|<90>

2u --> 100

1u --> 50

(a)

L (at first) = 5u + 10

5u + 100 --> (5 × 50) + 10

= 250 + 10

= **$260**

(b)

Sum of money (K + L) (at first) = 12u + 10

12u + 10 --> (12 × 50) + 10

= 600 + 10

= **$610**

=========

Trust this helps.

Do let me know again if there's further clarification.

Cheers,

Edward