We must take into account the following change of units:

Applying the change of units we have that the electric consumption for 1 year is given by:

Then, the total cost is given by:
Answer:
the cost of operating a 3.00-w electric clock for a year is:
$ 2.3652
The greatest common factor would be 16
83 + 58 = 141
55 + 68 = 123
92 + 69 = 161
48 + 72 = 120
69 + 77 = 146
95 + 88 = 183
78 + 43 = 121
86 + 77 = 163
79 + 47 = 126
74 + 59 = 133
85 + 94 = 179
69 + 78 = 147
91 + 89 = 180
48 + 95 = 143
66 + 45 = 111
73 + 86 = 159
98 + 74 = 172
23 + 79 = 102
163 - 125 = 38
243 - 74 = 169
208 - 92 = 116
262 - 77 = 185
122 - 86 = 36
197 - 82 = 115
159 - 41 = 118
299 - 151 = 148
181 - 87 = 94
196 - 159 = 37
232 - 168 = 64
165 - 76 = 89
241 - 85 = 156
149 - 38 = 111
184 - 95 = 89
124 - 67 = 57
142 - 96 = 46
272 - 119 = 153
261 - 95 = 166
225 - 88 = 137
p.s a calculator does exist.
Let:
x = cost of senior citizen ticket
y = cost of student ticket
4x + 5y = 102
7x + 5y = 126
4x + 5y = 102
4x = 102 - 5y
x = (102 - 5y)/4
x = 102/4 - 5y/4
7x + 5y = 126
7(102/4 - 5y/4) + 5y = 126
(714/4 - 35y/4) + 5y = 126
-35y/4 + 5y = 126 - 714/4
note:
-35y/4 = -8.75y
714/4 = 178.5
-8.75y + 5y = 126 - 178.5
-3.75y = -52.5
y = -52.5/-3.75
y = 14
x = 102/4 - 5y/4
x = 102/4 - 5(14)/4
x = 8
x = cost of senior citizen ticket = $8/ea
y = cost of student ticket = $14/ea