How do you solve #1/5 + (3x)/15=4/5#?

1 Answer
Aug 26, 2015

Answer:

#x = 3#

Explanation:

Your ultimate goal is to isolate #x# on one side of the equation, so start by getting rid of the denominators.

Notice that you can multiply #1/5# and #4/5# by #1 = 3/3# to get

#1/5 * 3/3 + (3x)/15 = 4/5 * 3/3#

#3/15 + (3x)/15 = 12/15#

All the terms have the same denominator, which means that you can write

#(3 + 3x)/15 = 12/15#

#(3 + 3x) * color(red)(cancel(color(black)(1/15))) = 12 * color(red)(cancel(color(black)(1/15)))#

#3 + 3x = 12#

Next, add #-3# to both sides of the equation

#color(red)(cancel(color(black)(3))) - color(red)(cancel(color(black)(3))) + 3x = 12 -3 #

#3x = 9#

Finally, divide both sides by #3# to get #x# alone on the left-hand side of the equation

#(color(red)(cancel(color(black)(3)))x)/color(red)(cancel(color(black)(3))) = 9/3#

#x = color(green)(3)#