You might be able to do direct substitution.
Answer:

Step-by-step explanation:
3x - 6y = 24
Divide both sides by 6:
(3/6)x - (6/6)y = 24/6
Simplify:
(1/2)x - y = 4
Move y to the right side, 4 to the left side, and change sign of y and 4:
(1/2)x - 4 = y
Rearrange both sides:
y= (1/2)x - 4
Hope this helps!
:)
If you would like to calculate 1/10 of what number is 0.04, you can do this using the following steps:
1/10 of what number is 0.04
1/10 * x = 0.04 /*10
x = 0.04 * 10
x = 0.4
Result: 1/10 of 0.4 is 0.04.
300 grams = 0.3 kilograms