I think you can use cosine rule if only the lines that form the <52 are equal.
The equation that has an infinite number of solutions is 
<h3>How to determine the equation?</h3>
An equation that has an infinite number of solutions would be in the form
a = a
This means that both sides of the equation would be the same
Start by simplifying the options
3(x – 1) = x + 2(x + 1) + 1
3x - 3 = x + 3x + 2 + 1
3x - 3 = 4x + 3
Evaluate
x = 6 ----- one solution
x – 4(x + 1) = –3(x + 1) + 1
x - 4x - 4 = -3x - 3 + 1
-3x - 4 = -3x - 2
-4 = -2 ---- no solution

2x + 3 = 2x + 1 + 2
2x + 3 = 2x + 3
Subtract 2x
3 = 3 ---- infinite solution
Hence, the equation that has an infinite number of solutions is 
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<u>Complete question</u>
Which equation has infinite solutions?
3(x – 1) = x + 2(x + 1) + 1
x – 4(x + 1) = –3(x + 1) + 1


Answer: a) 
Step-by-step explanation:
Since we have given that

a.) Find the inverse of f(x) and name it g(x).
Let f(x) = y
So, it becomes
Switching x to y , we get


b) . Use composition to show that f(x) and g(x) are inverses of each other.

Similarly,

so, both are inverses of each other.
c) Draw the graphs of f(x) and g(x) on the same coordinate plane.
As shown below in the graph , Since for inverse function we need an axis of symmetry i.e. y=x
And both f(x) and g(x) are symmetry to y=x.
∴ f(x) and g(x) are inverses of each other.
<span>2x + x = 12
=> x =12/3 =4
so, original number is 84. </span>