x+y=10
x+2y=14
x is common in both so u have to subtract the second one from 1st
x-x + y-2y = 10-14
-y = -4
y=4
which means bottle of water (y) = 4
and then substitute 4 in equation (x+y=10 or x+2y=10)
x + 4 = 10
x=6
<em>To solve for a variable, you just need to isolate the variable to one side.</em>
<h3>7.</h3>
For this, just divide both sides by r and <u>your answer will be
</u>
<h3>8.</h3>
For this, divide both sides by nR and <u>your answer will be
</u>
<h3>9.</h3>
Firstly, multiply both sides by T: 
Next, subtract FV on both sides of the equation: 
Lastly, multiply both sides by -1, and <u>your answer will be
</u>
<h3>10.</h3>
Firstly, multiply both sides by 1000: 
Lastly, divide both sides by tc and <u>your answer will be
</u>