# ACT Math 1.3 Elementary Algebra

ACT Math Elementary Algebra: Drill 1, Problem 3. Solve for y using substitution.

ACT Math | Elementary Algebra |

ACT Mathematics | Elementary Algebra |

Elementary Algebra | Evaluation of algebraic expressions through substitution Linear equations Substitution |

Foreign Language | Arabic Subtitled Chinese Subtitled Korean Subtitled Spanish Subtitled |

Language | English Language |

Polynomials | Multiplying Polynomials |

Product Type | ACT Math |

### Transcript

Questions like this one are algebra's version of... puzzles. Except you don't have to

worry about getting that cardboard dust all over yourself.

The key is to isolate one of the variables cleanly...

...i.e. figure out just what y equals and then shove that result into the other equation

so we can get a real answer.

It doesn't matter which equation we solve, but let's start with the second because...

it's there. And we already have a variable all by its lonesome.

We can rewrite it as x equals 12 minus 3y.

So now, everywhere we see an "x" we can just substitute "12 minus 3y."

If we do so in the first equation, we get 2 times the quantity 12 minus 3y... plus the

4y and equals 16.

Distribute the 2 and we have 24 minus 6y plus 4y equals 16.

Simplify to get 8 minus 2y equals zero...

...and then 8 = 2y.

Then if we divide both sides by 2 and we get y equals... 4.

Answer C.

As in, "Cardboard dust."