How to improve myself.....in maths

I make alot of careless mistakes in maths.To stop that,after finishing a paper,i must CHECK CHECK and CHECK.I must also do more revision and correct all of my previous mistakes...especially those on positive and negative numbers

Praveen

Chapter 4: Algebra Puzzle

3x3 Grid Puzzle

My Solution: 

Let X be the value of 1 Pen

Let Y be the value of 1 Star

Let Z be the value of 1 Gear

Value of 1 Pen

3X = 27

so,

X = 9

The value of 1 pen is 9

Value of 1 Star

Y+Y+X=41

Y+Y= 41-9

        =32


Y=32/2
   =16


The value of 1 Star is 16


Value of 1 Gear


X+2Z=43
2Z=43-9
    =34

Z=34/2
   =17

The value of 1 gear is 17.

3x4 Grid Puzzle

Let X be the value of 1 Apple
Let Y be the value of 1 Car
Let Z be the value of 1 Ladybug


X+X+X+Y=68
Y+Y+Y+Z=100
Z+Z+Z+Y=92

Y+Y+Y+Y+Z+Z+Z+Z=100+92
                                    =192

4Y+4Z=192
Y+Z=192/4
       =48

Y+Y+Y+Z=100
Y+Z=48
so,
Y+Y=100-48
        =52

Y=52/2
   =26

The value of 1 car is 26

3X+Y=68
3X=68-26

    =42

X=42/3

   =14

The value of 1 apple is 14

Y+Y+Z=74

Y+Y=52

74-2Y=74-52

         =22

The value of 1 ladybug is 22