Here is the equation: x+(x+20) = 120
Since you can't combine anything yet, its x+x+20=120
You need to get x by itself
Minus 20 from both sides
Its x+x=100 now
Combine the x's which is now 2x
Now divide 100 by 2 which is 50
x=50
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Lets check:
50+(50+20)=120
Now combine the numbers in the parentheses
Its now 50+70=120
50+70=120 and 70-50=20
As you can see, he ran 50 minutes the first day and 70 minutes the second day
Seeing as there are three coins, which means there are 3 heads and 3 tails.There's only a 50% chance it'll land on either side one one coin. I believe the chances to get two heads, and one tail would be somewhere around 80%, since there are only 8 possible outcomes.
