Answer:
s=14
Step-by-step explanation:
Let's first get rid of denominators by multiplying both sides by 6. Then it's simply a matter of adding up what's left and simplifying.
[tex]6(\frac23s+\frac56s) = 6(21)\\4s+5s=126\\9s=126 \rightarrow s = \frac{126}9 = 14[/tex]
