Opposite sides are the same length.
4y=y+18
4y-y=18
y= 18/3 = 6
DC = 6+18=24
In the given parallelogram ABCD, the property of parallelograms states that opposite sides are of equal length. Therefore, the length of side AD is equal to the length of side BC, and the length of side DC is equal to the length of side AB.
To determine the length of DC, an equation is set up using the information provided in the diagram. It is given that 4y represents the length of side AD, and y+18 represents the length of side BC. Equating these two expressions, we have 4y=y+18.
By isolating the variable y, we subtract y from both sides of the equation, resulting in 3y=18. Solving for y, we find that y=6. Now that we know the value of y, we can find the length of DC by substituting it into the expression 4y+18, which gives 4(6)+18=24. Thus, the length of DC is determined to be 24 units.