Every number is already a fraction, it just may not be written in the fraction form. 35 in the fraction written form is 35/1
1÷81 because you square it
From the setup of the problem, the "length of the top of the bookcase, measured along the attic ceiling" will be the hypotenuse of a right triangle, the length "AB". We have both the angle between AB and AC and the length of AC (3.24 meters), so we can use trigonometric identities.
The cosine of the 40 degree angle between AB and AC is equivalent to the length of AC divided by the length of AB. Equivalently, we have:

where "h", the hypotenuse, is the length we want. Rearranging the formula to solve for h we have that

which is 4.2295... meters. Converting to centimeters (multiplying by 100) we have that h = 422.95... centimeters, or if we round the value, h = 423 centimeters.
1:21 divide both digits by 9
Answer:
B: 210
C: 450
Step-by-step explanation:
You just need to multiply the two numbers overlapping in the box. For B, the two numbers for that box are 30 and 7, therefore you must multiply them together to get 210. For C, the numbers are 90 and 5, when multiplied equals 450. Hope that helps!