Answer:
The number of letters in the one street be 220 .
Step-by-step explanation:
As given
A postman has to deliver 450 letters .
The number of letters delivered in one street is twice the number delivered in other .
Let us assume that the number of letters delivered in second street be x.
Let us assume that the number of letters delivered in first street = 2x
As given
If he is left with 120 letters .
Thus
The number of letter delivered in one and other street = 450 - 120
= 330
Than the equation becomes
x + 2x = 330
3x = 330
x = 110
The number of letters in the one street = 2 × 110
= 220
Therefore the number of letters delivered in first street be 220.