The answer to the question is A by using definitions of logs
Answer:
r=s-t ÷ 2
Step-by-step explanation:
r2=s-t
r2÷2= s-t ÷2
r=s-t ÷2

The last choice is appropriate.
Answer:
A
Step-by-step explanation:
7=8.96
5=??
(5×8.96)÷7= 6.4
which is shown by A
Let nails 7/pound=N1
nails 3/pound=N2
let N1=x
N2=6
then total=x+6
7x+6*3=(x+6)*4
7x+18=4x+24
3x=6
x=2
so 2 pounds on Nails costing 7/pound must be added