Amachine can insert letters in envelopes at the rate of 120 per minute. another machine can stamp the envelopes at the rate of 3 per second. how many such stamping machines are needed to keep up with 18 inserting machines of this kind?
(a) 12
(b) 16
(c) 20
(d) 22
(e) 24

step-by-step explanation:

in the absence of parentheses, i will have to make some assumptions:   i interpret your (3x+5/y^6)(4y^3/5)​ to mean:

3x + 5     4y^(3/5)       (3x + 5)(4)

* =

    y^6             1               y^(6-3/5)

if this is not what you expected, repost your question using parentheses to indicate whether you meant

4y^3

    or   4y^(3/5)

    5