Which number goes in the box to make this a true number sentence? 34 × 45 = (34 × 40) + ( × 5)

Let's let "n" be the number tht we're looking for.....so we have....

34 × 45 = (34 × 40) + (n × 5)      .....        simplifying, we have

1530 = 1360 + (n X 5)                  ......       subtract 1360 from both sides

170 = (n X 5 )                               .......      divide both sides by 5

34   =  n 

And that's the number we're looking for.....