5/11×4/15= 9/14×5/12= 18×2/9= 15×9/10= 3/7×21= 4/9×6= 15×2ц3/5= 1ц3/7×2ц4/5=

5/11×4/15 = (5×4)/(11×15) = 4/(11×3) = 4/33
9/14×5/12 = (9×5)/(14×12) = (3×5)/(14×4) = 15/56
18×2/9 = (18×2)/9 = 2×2 = 4
15×9/10 = (15×9)/10 = (3×9)/2 = 27/2
3/7 × 21 = (3×21)/7 = 3×3 = 9
4/9×6 = (4×6)/9 = 4×2 = 8
Хз что за «ц»