Solve with substitution
y = x - 15
y = 4x

(-5, -20)

General Formulas and Concepts:

Pre-Algebra

Order of Operations: BPEMDAS

to Right  

Equality Properties

Multiplication Property of EqualityDivision Property of EqualityAddition Property of EqualitySubtraction Property of Equality

Algebra I

Coordinates (x, y)Solving systems of equations using substitution/elimination

Step-by-step explanation:

Step 1: Define

y = x - 15

y = 4x

Step 2: Solve for x

Substitution

Substitute in y:                                                                                                4x = x - 15[Subtraction Property of Equality] Subtract x on both sides:                      3x = -15[Division Property of Equality] Divide 3 on both sides:                                x = -5

Step 3: Solve for y

Define original equation:                                                                               y = 4xSubstitute in x:                                                                                                y = 4(-5)Multiply:                                                                                                           y = -20

The answer is e &