First you should be able to figure out that,
So Mr Gabriel bought 100 packages.
Since each package contains 15 pens,
Total number of pens
..........................I'm just trying
The volume is 750.
10X6X12.5
The answer of this math question is C) X= -0.2
1: x + 8.23 = -5.14
Subtract 8.23 from both sides
x = -13.37
2: 4/9x = 32
Multiply both sides by 9 (basically, 4 is being divided by 9, so the opposite is to multiply).
(9 times 4, then divided by 9 is 4)
4x = 288
Divide both sides by 4 to isolate x
x = 72