what is the answer to 18-4t/0.5=20 ?
Perhaps it was the fraction that put you off, or was it the decimal in the denominator. I guess you want to find the value of t. Let's get rid of the fraction by multiplying both sides of the equation by 0.5. It's not clear in the question whether the problem is 18-(4t/0.5)=20 or (18-4t)/0.5=20. The brackets tell us what has to be worked out first. I'm going to provide solutions whichever one of these is the problem.
Multiplying both sides by 0.5 we get 18*0.5-4t=20*0.5 giving us 9-4t=10. The decimals have been swallowed up in the multiplication. 0.5 is the same as 1/2, but if you didn't know that, multiply by 5 and move the decimal point back one place. So, for example, 5*18=90. The decimal point invisibly sits after 90, so moving it back a place makes it 9.0 which is just 9. So 9-4t=10. We need to get the numbers on one side of the equation and the unknown on the other side. At this stage we don't want to separate 4 from 4t. OK, let's keep the unknown on the left, so we get -4t=10-9, giving us -4t=1. When we move things from one side of an equation to the other plus becomes minus, and minus becomes plus, multiply becomes divide, and divide becomes multiply. So this is the same as 4t=-1, and t=-1/4.
Multiply both sides by 0.5 and we get 18-4t=20*0.5, in other words 18-4t=10. Let's separate the unknown from the numbers, but this time we'll take the unknown over to the right (it doesn't matter which side really). So we get 18-10=4t. Therefore 8=4t, the same as 4t=8, so t=2. That looks like the simpler of the two answers, so my guess is that it's what the question really was, don't you think? It's important that questions are written correctly because, as you can see, we came up with two quite different answers. Read More: ...