Answer:
[tex] \boxed{\sf r = - 4} [/tex]
Step-by-step explanation:
[tex] \sf Solve \: for \: r: \\ \sf \implies - 1.5(4 - r) = - 12 \\ \\ \sf Divide \: both \: sides \: of \: - 1.5(4 - r) = - 12 \: by \: - 1.5 : \\ \sf \implies \frac{ - 1.5(4 - r)}{ - 1.5} = \frac{ - 12}{ - 1.5} \\ \\ \sf \frac{ \cancel{ - 1.5}}{ \cancel{ - 1.5}} = 1 : \\ \sf \implies 4 - r = \frac{ - 20}{ - 1.5} \\ \\ \sf \frac{ - 20}{ - 1.5} = 8 : \\ \sf \implies 4 - r = 8 \\ \\ \sf Subtract \: 4 \: from \: both \: sides: \\ \sf \implies (4 - \boxed{ \sf 4}) - r = 8 - \boxed{ \sf 4} \\ \\ \sf 4 - 4 = 0 : \\ \sf \implies - r = 8 - 4 \\ \\ \sf 8 - 4 = 4 : \\ \sf \implies - r = \boxed{ \sf 4} \\ \\ \sf Multiply \: both \: sides \: of - r = 4 \: by \: - 1: \\ \sf \implies - r \times ( - 1) = 4 \times ( - 1) \\ \\ \sf - r \times ( - 1) = r : \\ \sf \implies r = 4 \times ( - 1) \\ \\ \sf \implies r = - 4[/tex]
