1) 5/9+1ц5/7×(4ц2/3-2ц5/8)÷1ц3/4= 5/9+12/7×((4-2)+(2/3-5/8))÷7/4= 5/9+(12/7×2ц1/24)÷7/4= 5/9+(12/7×49/24)÷7/4= 5/9+7/2×4/7=5/9+4/2= 5/9+2=2ц5/9
2) 2-3ц1/7×(2-1ц9/11)÷8/21= 2-22/7×(1ц11/11-1ц9/11)÷8/21= 2-(22/7×2/11)÷8/21= 2-4/7×21/8= 2-3/2= 1ц2/2-1ц1/2=1/2