A powerful way to find out is to solve the equation. Let's try that.
3 (d + 11) = 6 (d + 33)
Eliminate the parentheses: 3d + 33 = 6d + 198
Subtract 3d from each side: 33 = 3d + 198
Subtract 198 from each side: -165 = 3d
Divide each side by 3 : - 55 = d
There it is ... the solution to the original equation.
'd' has to be -55, otherwise the original equation isn't a true statement.
-55 is the ONLY number that 'd' can be. If you write in any other number
for 'd', the equation will be false.
For example, less see what the equation says when d=2 :
3(2 + 11) = 6(2 + 33)
3( 13 ) = 6( 35 )
39 = 210
Is that a true statement ? Is 39 equal to 210 ?
No. 39 and 210 are not equal. They are different.
So the equation is not true when d = 2 .
The equation is true ONLY when d = -55 .
The equation has exactly one solution.
