How do you solve #x = y + 3# and #2x + y = 9# using substitution?

1 Answer
Jarni Renz
Mar 14, 2016

You are given 2 variables, decide which variable you want to be substituted and what equation will be your base equation to plug in your value.

Explanation:

1, In this case, #2x + y =9# may be use as your base equation and #x=y+3#, since this equation does not need rearrangement to find the value of #x#, will be used to substitute (for x from your base equation) to find the value of #y#;
2. From your base equation, substitute the value of #x#;
#2color(red)x +y=9#; where #x=y+3# forming like this
#2color(red)((y+3))+y=9#
3. Now, as reflected above, you have only one variable and you can now find the value #y#;
4. Then simplify the equation and combine like terms if applicable until you can arrive the value of y;
#2(y+3)+y=9#
#2y +6+y=9#
#3y+6=9#
5. Isolate the term with #y# from the numerical value by subtracting 6 both sides of the equation;
6. The value of y = 1
7. To find the value of #x#, you can use either of the equations and plug in the value of #y#;
8. Always remember to plug in values of #y# and #x# to check if both sides of the 2 equations are balanced.

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