3c - 4d ; c = 5 ; d = 1/2
Remember this order of operation:
PEMDAS (Parenthesis, Exponent, Multiply, Divide, Add, Subtract)
3(5) - 4(1/2) Substitute the letters by its value
⇒15 - (4*1)/2
In multiplying fractions, numerator * numerator / denominator * denominator = in this case, 4/1 * 1/2 ; 4 and 1 are the numerators; 1 and 2 are the denominators.
⇒15 - 4/2 After multiplication, perform division
⇒15 - 2 no addition, so proceed to subtraction.
⇒13
3c - 4d = 13
