How many $$8$$ digit numbers are there that contain both a $$5$$ and a $$6$$?

Number of $$8$$ digit numbers containing both a $$5$$ and a $$6$$

= Number of $$8$$ digit numbers - Number of $$8$$ digit numbers lacking both a $$5$$ and a $$6$$

$$=90000000-7\ast {8}^{7}$$

$$=75319936$$

Does this seem right?

Number of $$8$$ digit numbers containing both a $$5$$ and a $$6$$

= Number of $$8$$ digit numbers - Number of $$8$$ digit numbers lacking both a $$5$$ and a $$6$$

$$=90000000-7\ast {8}^{7}$$

$$=75319936$$

Does this seem right?