Two angles are supplementary with measures m∠ACB=4x° and m∠BCD=(6x+50)° . What is the measure of ∠ACB ?

The sum of supplementary angles is always 180 degrees.

So, we have the equation:

m∠ACB + m∠BCD = 180

Substituting the given values, we get:

4x + (6x + 50) = 180

Combining like terms,

10x + 50 = 180

Subtracting 50 from both sides,

10x = 130

Dividing both sides by 10,

x = 13

Finally, we can find the measure of ∠ACB by substituting the value of x into the equation for m∠ACB:

m∠ACB = 4x

m∠ACB = 4 * 13

m∠ACB = 52 degrees. Answer: \boxed{52}.