Help...homework help...math problem?

Question

how do you do solving equations by using addition and subtracting,but when you have a fraction?

here is one of the problems....

r+1/5=9/10

how would you do that?

i don't remember how to do an add or subtract problem,with a fraction.

please could you break it down too.

also what does "and"mean in a math term?

Answer 1

first you move 1/5  to the other side and it becomes negative. like this

r=9/10-1/5 then you find the lowest common multiple(l.c.m) which is 10.

9-2/10=7/10 or you change them to decimal and then do the subtraction like this r=9/10(which is also 0.9)-1/5(which is also 0.2)=0.7

Answer 2

First of all, you need to isolate the "r" (witch means to get it on one side of the equation). So to do that, you have to subtract 1/5 from both sides of the equation. r+1/5-1/5=9/10-1/5. The +1/5 and the -1/5 cancel out so you have r=9/10-1/5. now you have to get the denominator (the bottom number) of both numbers to be the same. To do this you have to find a number both of the numbers can multiply into. In this case its easy, the number is 10 (10 goes into 10 one time, and five goes into 10 two times). so r=9/10-?/10. To find the number on top of the second ten, you find the number you multiplied the original denominator by (in this case 2) and multiply the original numerator by that. so r=9/10-2/10. now its basic subtraction. 9-2=7, so r=7/10. I hope it makes sense, =]