1/7+2x/3=(15x-3)/21 make all terms have a common denominator of 21
3+14x=15x-3 subtract 3 from both sides
14x=15x-6 subtract 15x from both sides
-x=-6 divide both sides by -1
x=6
*Notice the use of parentheses in this format to make it clear what the numerators and denominators are...
It takes Selma 1/6 of a hour to run 3/4 miles.
Just multiply 3/4 by 6 to get 18/4 which is 4.5 miles or 4 1/2 mile
(7+x)+x=15
I did trial and error to get x=4.
When a negative number multiplies a negative number, it becomes positive
since it is multiplication, just multiply across, you do not need same denominators
5/8 x 16/25 = 80/200
80/200 = 40/100 = 20/50 = 2/5
2/5 is your answer
hope this helps