Because 5x4 is 20 but 5x1/4 is 1,25.
5 x 1 = 5... / 4 = 1,25
Or ... -> 1/4 = 0,25 * 5 = 1,25
;)
J/-2 + 7 = -12 multiply both sides with 2
-j + 14 = -24 move -14 to the other side and change sign
-j= -24 - 14
-j = -38 and if you divide -38 with -1 you get + 38
j=38
If this is supposed to be

Then this can simply be reduced to

by the double angle formula for cosine
Volume is legnth times widht times height
lenght=2x-1
width=x-2
height=x+1
multiply all together
use mass distributive property
distributive=a(b+c)=ab+ac so extending that
(a+c)(c+c)=(a+b)(c)+(a+b)(d) then keep distributing so
(2x-1)(x-2)(x+1)
do each one seperately
do the first two first and put the other one (x+1) to the side for later
(2x-1)(x-2)=(2x-1)(x)+(2x-1)(-2)=(2x^2-x)+(-4x+2)=2x^2-5x+2
then do the other one
(x+1)(2x^2-5x+2)=(x)(2x^2-5x+2)+(1)(2x^2-5x+2)=(2x^3-5x^2+2x)+(2x^2-5x+2)=2x^3-3x^2-3x+2
the lasst form is 2x^3-3x^2-3x+2