Equation Help

My daughter needs to solve 3x + 5 = 20 and show the work.

Here is an example of one problem she completed in class:

5x - 10 = 20
+10 = +10
20 30 / 5
x=6

mcfadm said:

My daughter needs to solve 3x + 5 = 20 and show the work.

Here is an example of one problem she completed in class:

5x - 10 = 20 <<< Get the term containing x all by itself on one side of the equation.
+10 = +10 <<< She added 10 to both sides to eliminate the -10 from the left side.
5x.....= 30 <<< I would add this step which is the result of the previous addition.
5x/5 = 30/5 <<< We divide by the coefficient of the variable to get one x. (5 of 'em divided by 5 quals one of em).
....x = 6 <<<(5x/5=x and 30/5=6)
20 30 / 5 <<< I don't know what the 20 is.

Click to expand...

Check...
5(6) - 10 = 20???
5(6)=30 therefore, we have...
30 - 10 = 20
30-10 = 20 therefore we have...
20 = 20 >>>> it checks. x=6 is our solution.

So, the steps are...
1) Isolate the term containing the variable by adding or subtracting the same things from both sides of the equation. It's okay to add or subtract a term with a variable if there are more than one of such in the equation.
2) Once you have the term containing the variable on one side of the equation and one term without the variable on the other side, then divide both sides of the equation by the coefficient of the variable.
3) Check your answer by substituting the value obtained for the variable back into the original equation in place of the variable. Then do the arithmetic on each side of the equation to see if they are equal. If they are not equal you either have the wrong solution or you made a mistake in the arithmetic while checking.

This was very helpful. Thank you.