Basic College Mathematics (9th Edition)

$\frac{ -3s - t - 4 }{-s + 6 + t }$ Replace s with -1 and t = -13 $\frac{ -3(-1) - (-13) - 4 }{-(-1) + 6 + (-13) }$ Do all the multiplications first $\frac{ 3 + 13 - 4 }{1 + 6 - 13}$ Addition and subtraction from left to right the numerator and denominator $\frac{16 - 4}{7 - 13}$ = $\frac{12}{-6}$ Dividing two numbers with the opposite sign gives negative number -2