d = r · t ⇒ t = d/r
going
t = 54/(r + 4)
coming
t = 30/(r - 4)
54/(r + 4) = 30/(r - 4) times are equal
54(r - 4) = 30(r + 4) product means/extremes
54r - 216 = 30r + 120 distribute
24r - 216 = 120 subtract 30r from both sides
24r = 336 add 216 to both sides
r = 14 divide both sides by 24
Alfonso bikes at 24 mph.
57 - 4t > = 13.....subtract 57 from both sides
-4t > = 13 - 57
-4t > = - 44 ...divide both sides by -4, and change the inequality sign
t < = -44 / -4
t < = 11
u solve inequalities much like u do equations except for one very important rule. In an inequality, if u divide/multiply by a negative number, u have to change the inequality sign.
