Simultaneously 7748

The monitor screen is blank. Four new wheels appear on the screen every seven seconds when the beep sounds. On the contrary, three wheels disappear from the screen every eleven seconds. If both actions should take place simultaneously, the number of circles on the screen will not change.
A) Specify the number of circles on the screen 1 minute after the beep.
B) Specify the number of circles on the screen 5 minutes after the beep.

Correct answer:

a =  17
b =  84

Step-by-step explanation:

$a=4-3+4+4-3+4-3+4+4-3+4-3+4=17$

$b=4-3+4+4-3+4-3+4+4-3+4-3+4+4-3+4+0+4-3+4+4-3+4-3+4+4-3+4-3+4+4-3+4+0+4-3+4+4-3+4-3+4+4-3+4-3+4+4-3+4+0+4-3+4+4-3+4-3+4+4-3+4-3+4+4-3=84$

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