Question 1159116
<br>
Consider the least common multiple of the two given times, which is 210 seconds.<br>
In 210 seconds, Lester can lace up 210/30 = 7 shoes, and Ralph can lace up 210/35 = 6 shoes.  So in every 210 seconds the two of them can lace up 7+6=13 shoes.<br>
They need to lace up 260 shoes.  260/13 = 20; so the amount of time it will take them to lace up the 260 shoes is 20*210 = 4200 seconds, or 70 minutes.<br>