5x=1s 10s=1b ​50b=?x

If you know that  5x = 1s  and  10s = 1b,

then you can multiply the first equation to get  50x = 10s,

and you can tie this equation to the second equation to get:  50x = 10s = 1b.

 

Now, if you want 50b:

Multiply  50x = 10s = 1b  by 50  to get  2500x = 50s = 50b,

so  50b  = 2500x.