Mercury orbits the sun in 87 and 24/50 venus orbits the sun in 224 and 7/10 earthdays and mars orbits the sun in 686 and 49/50 days write each mixed number as a decimal

Mercury: 87 24/25
Venus 224 7/10
Mars 686 49/50

All we need to do is to convert fractions so they have a denominator of 10, 100, 1000 etc.

87 24/25 = 87 96/100
224 7/10 stays the same
686 49/50 = 686 98/100

Now we can easily convert them into decimals:

Mercury: 87.96
Venus: 224.7
Mars: 686.98

The answer would be b