Since angles ∠ACB and ∠BCD are supplementary, their measures add up to 180 degrees:
\[ m∠ACB + m∠BCD = 180° \]
Substituting the expressions for the angles:
\[ (x + 28) + (x + 48) = 180 \]
Combining like terms:
\[ 2x + 76 = 180 \]
Next, we solve for \(x\):
\[ 2x = 180 - 76 \] \[ 2x = 104 \] \[ x = 52 \]
Now we can find \(m∠BCD\):
\[ m∠BCD = x + 48 = 52 + 48 = 100° \]
So, the measure of angle \(BCD\) is 100°.