answer
s=45 units
bc=434 units
explanation
Find the value of s
In a Rhombus all sides are congruent so
AB=BC=CD=DA
AB=9s+29
CD=10s−16
equate AB and CD
9s+29=10s−16
Combine like term
10s−9s=29+16
s= 45 units
the value of s is 45 units
Find the value of side AB
AB=9s+29AB=9s+29
substitute the value of s
AB=9*45+29=434 units
Remember that the sides are congruent
AB=BC=CD=DA
therefore
The length of the side BC is 434 units
