Originally Posted by

**sdfghnjhgfdcfvgbhnjhgfdsx** well im not sure. if we remove the mixed fraction and compare the 2:

7/1 + 11/4

and

3/4 + 2/5 - 7/10

the 1st one multiplied 7/1 both by 4 LCM. but in the other task what's confusing me is they didnt miltiply the fractions by the LCM 20 like they did in the 1st one. Instead they used 20 as the denominator then mulitplied the nemerator by a number that would result in 20. Why didnt they multiply both the numerators and denomerators by 20 like the previous?