what we have to solve is:
[tex] \frac{4}{5} = \frac{x}{10} [/tex]
we should multiply both sides by10, to get the "x" by itself:
[tex] \frac{4*10}{5} = \frac{x} [/tex]
[tex] \frac{4*2}{1} = \frac{x} [/tex]
[tex] 8 = \frac{x} [/tex]
so there are 8 tenths in this number!
