we will assume that Omar collected tens,fives,and ones only

let

x = the number of ones

y = the number of fives

z = the number of tens

One Saturday Omar collected from his newspaper customers twice as many dollar bills as fives

x = 2y

and one fewer ten than fives

z = y - 1

Omar collected $58

x + 5y +10z = 58

plug x = 2y and z = y - 1 into x + 5y +10z = 58

we have

2y + 5y + 10(y - 1) = 58

by solving we find

y = 4

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x = 2*4

x = 8

z = 4 - 1

z = 3

Omar collected 8 ones, 4 fives and 3 tens.