解:210÷30-170÷30+50÷30等于( 3 )
∵已知需求出210÷30-170÷30+50÷30等于多少
∴210 ÷ 30-170 ÷ 30 + 50 ÷ 30
= 210 × 1/30 - 170 × 1/30 + 50 × 1/30
= 210/30 - 170/30 + 50/30
= 7 - 17/3 + 5/3
= 21/3 - 17/3 + 5/3
= 4/3 + 5/3
= 9/3
= 3
答:210÷30-170÷30+50÷30等于3