I NEED TO REPLACE MY CONCRETE IN 7 YEARS. THE TOTAL COST IS $15,000, HOW MUCH DO I NEED TO SAVE ANNUALLY AT 5%.

750  

Step-by-step explanation:

Because you need to multiply the total cost times the annually  percent which is 5% and 5% times 15,000 is 750.

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