Simplify 67c − 59d − 12 c + 13d .
To simplify 67c − 59d − 12c + 13d, we can combine like terms.
The terms with c are 67c and -12c, so they can be combined to give 55c.
The terms with d are -59d and 13d, so they can be combined to give -46d.
Therefore, the simplified expression is 55c - 46d.