Solution:
(a) Cash to be accounted for exceeds cash on hand by $52.78. 
 Cash to be accounted for is $7,146.30 . 
That means cash on hand is short by $52.78. 
 Dr Cash $7,487.51 
 Dr Cash over and short $57.71 
 Cr Sales $7,545.22 
 (b) Cash on hand exceeds cash to be accounted for by $29.45. 
 That means you have a cash overage of $29.45
 Dr Cash $7,590.10 
 Cr Sales $7,545.22 
 Cr Cash over and short $29.45