Answer:
I think the answer is C sorry if I'm wrong but hope I helped
Step-by-step explanation:
step 1. 4x + 27 + 3x = 90 (definition of a rectangle)
step 2. 7x = 63 (collect like terms. subtract 27 from both sides)
step 3. x = 9 (divide both sides by 7)
If you sketch the triangle, you need to understand that 12 is the length of opposite side (opposite to theta). Then the longest side is 13 is the hypotenuse. The other side with length 5 is the adjacent side. Thus from the definition of sin(theta)=opposite side/hypotenuse=12/13. A question for you, what is cos(theta)? cos(theta)=5/15 and tan(theta)=12/5
The acceleration of the bookshelf is equal to 1.30 
<u>Given the following data:</u>
- Mass of bookshelf = 51.5 kilogram
To determine the acceleration of the bookshelf, we would apply Newton's Second Law of Motion:
Newton's Second Law of Motion states that the acceleration of an object is directly proportional to the net force acting on the object while being inversely proportional to its mass.
Mathematically, Newton's Second Law of Motion is given by this formula;

Substituting the given parameters into the formula, we have;

Acceleration = 1.30 
Read more on net force here: brainly.com/question/1121817