Write each sentence using mathematical symbols:

(a) Twice $c$, minus $3$, is the same as $16$:

(b) Four more than the product of $6$ and $d$ is $9$:

Note: The middle answer blank in both parts is for you to enter "<=", "<", "=", ">", or ">=" for "less than or equal to", "less than", "equals", "greater than", or "greater than or equal to", respectively.