About 1: 10 for the bones in your body are your in your skull your hands have about 1/4 of the bones in your body right and solve an equation to find the fraction of the bones in your body that are in your hands or skull

So to get the answer, we just add the number of bones in your hands and bones in your skull
1/4 (bones in hands) + 1/10 (bones in skull)
we can only add fractions that have the same denominator (bottom number in a fraction) so we change the numbers to have a common denominator:
5/20 + 2/20 = 7/20
so 7/20 of your bones are in your hands or skull