67/12+(5 3/40-4 8/15) 7 11/15-(3 9/20+1/30) ,! : *

79/12 +(203/40 - 68/15)=79/12+(203*3 - 68*8)/120=79/12+65/120=79/12+13/24=(79*2+13)/24=171/24=7  3/24=7 1/8

7 11/15- (69/20 + 1/30)=116/15 -(69*3+2)/60=116/15- 209/60=(116*4-209)/60= 255/60 = 51/12=17/4=4 1/4,