How do you subtract #\frac { 7a - 2} { 21} - \frac { 5a + 6} { 15}#?

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Answer 1 · 2017-07-30T20:20:45

#(-52)/105#

#(7a-2)/21 - (5a+6)/15#

To add fractions we need to have a common denominator to do so.
We can use prime factors to find the LCD.

#(7a-2)/(3xx7) - (5a+6)/(3xx5)" "larr LCD = 3 xx5xx7#

Make equivalent fractions

#=(5(7a-2)-7(5a+6))/(3xx5xx7)#

#=(35a-10 -35a-42)/(3xx5xx7)" "larr# now simplify

#=(-52)/105#