Well, that's incorrect because according to the Order of Operation [GEMS\BOMDAS\PEMDAS etc.], that -7 has to be distributed amongst all the other terms in parentheses. Besides, you did the wrong operation when you inserted that subtraction symbol in substitution of the parentheses, which means to MULTIPLY. So, the order goes as follows:
12 - 7[72]
-504 + 12 = -492 [OR 12 - 504]
-492 is your answer. You get it now?
Answer:
10
Step-by-step explanation:

(Простите, пожалуйста, мой английский. Русский не мой родной язык. Надеюсь, у вас есть способ перевести это решение. Если нет, возможно, прилагаемое изображение объяснит достаточно.)
Use the shell method. Each shell has a height of 3 - 3/4 <em>y</em> ², radius <em>y</em>, and thickness ∆<em>y</em>, thus contributing an area of 2<em>π</em> <em>y</em> (3 - 3/4 <em>y</em> ²). The total volume of the solid is going to be the sum of infinitely many such shells with 0 ≤ <em>y</em> ≤ 2, thus given by the integral

Or use the disk method. (In the attachment, assume the height is very small.) Each disk has a radius of √(4/3 <em>x</em>), thus contributing an area of <em>π</em> (√(4/3 <em>x</em>))² = 4<em>π</em>/3 <em>x</em>. The total volume of the solid is the sum of infinitely many such disks with 0 ≤ <em>x</em> ≤ 3, or by the integral

Using either method, the volume is 6<em>π</em> ≈ 18,85. I do not know why your textbook gives a solution of 90,43. Perhaps I've misunderstood what it is you're supposed to calculate? On the other hand, textbooks are known to have typographical errors from time to time...
five pairs of jeans should cost $67.5
Answer: You need a grade of 78 on the final exam to earn a final grade average of at least 87 in each grading system.
Step-by-step explanation:
(85 + 90 + 95 + x)÷ 4 =87
Simplify:
(270 + x) ÷ 4 = 87
Rearrange:
(x + 270) ÷ 4 = 87
Multiply terms to Reduce:
4((x + 270) ÷ 4) = 4 * 87
Cancel Multiplied terms in Denominator:
x + 270 = 4 * 87
Multiply:
x + 270 = 348
Subtract 270 on both sides of the equation:
x + 270 - 270 = 348 - 270
Simplify:
x = 78