Total number of quarters = 25
Total number of quarters he put into the bank = 7
To form the fraction of the quarters he put in the bank, we write it as:
[tex] \dfrac{\text { Number of quarters he put in the bank}}{\text {Total number of quarters he had}} = \dfrac{7}{25}[/tex]
[tex]\boxed {\boxed { \text{Answer: } \dfrac{7}{25} }}[/tex]