How do find the answer in subtractiion problem, when the top number is smaller than the bottom

It's going to become a negative number. You have to change the subtraction sign to addition, then take the second term and change it to a negative. Then you add it. Since one is positive and the other is negative, you have to subtract the absolute values (just the number without the negative sign) which ever Nemertea has the greater absolute value, that sign is going to be the sign for the answer. I know it's long and confusing. Sorry

Use a number line if you need 4/10 - 6/10 = - 2/10a simpler way is to do the opposite 6/10 - 4/10 = 2/10 then the answer would be the opposite as well. so, - 2/10