Answer : The number of letters engraved on each trophy must be 15.
Step-by-step explanation :
As we are given,
A trophy cost at one store = $ 12.50
Engraving cost per letter at one store = $ 0.40 × L
where, 'L' is number of letters.
A trophy cost at another store = $ 14.75
Engraving cost per letter at another store = $ 0.25 × L
Now we have to determine the number of letters must be engraved for the costs for this trophy at both stores to be the same.
$ 12.50 + ($ 0.40 × L) = $ 14.75 + ($ 0.25 × L)
($ 0.40 × L) - ($ 0.25 × L) = $ 14.75 - $ 12.50
$ 0.15 × L = $ 2.25
L = ($ 2.25) ÷ ($ 0.15)
L = 15
Therefore, the number of letters engraved on each trophy must be 15.