Formula calculation: ① a number of 23 minus 5 equals 5, how much is this number? ② 15 minus the product of 47 and 21, what is the quotient of the reciprocal of the difference divided by 13?

Formula calculation: ① a number of 23 minus 5 equals 5, how much is this number? ② 15 minus the product of 47 and 21, what is the quotient of the reciprocal of the difference divided by 13?

① (5 + 5) △ 23 = 10 △ 23 = 15; answer: the number is 10. ② 3 △ 15-47 × 21 = 3 △ 15-12 = 3 △ 3 = 1. Answer: the quotient is 1

1. What's the quotient if you remove 48 1 / 8 by 40% of 128? What's the quotient if you subtract the product of 4 / 7 and 21 from 2 and 15?

[48*（1/8）]/（128*40%）=15/128
2,
（1/5）/（15-4/7*21）=1/15

Twenty four times one fifth plus eight fifths minus twenty four times four fifths

24

What is 98 times four fifths plus 3 times four fifths minus five fifths

98 times four fifths plus 3 times four fifths minus one fifths
=4/5*(98+3-1)
=4/5*100
=80