Answer:
 a) $94
 b) S = 54 +8w
 c) 14 weeks
Step-by-step explanation:
The initial value of the account and its rate of change are given. These can be used to find the value at a time, or the time to reach a value.
For each of 5 weeks Johanna added $8, so will have added 5×$8 = $40 after 5 weeks. When that is added to the original $54, the balance will be ...
 account balance = $54 + $8 × 5
 account balance = $54 +40 = $94
Using S for the account balance, and w for the number of weeks, the above equation becomes ...
 S = 54 +8w
We can substitute 166 for S in the equation of part b to find the necessary value of w:
 166 = 54 +8w
 112 = 8w . . . . . . . . subtract 54
 14 = w . . . . . . . . divide by 8
14 weeks will have passed when Johanna has $166 in her account.