let 'x' and 'y' be the numbers and x > y

the difference of two numbers is 25

x - y = 25

the larger is one less than three times the smaller

x = 3y - 1

by solving the system of equations

x - y = 25

x = 3y - 1

we find

x = 38

y = 13

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the numbers are 38 and 13.