[tex]\frac{15t-9s}{3}=\frac{15t}{3}-\frac{9s}{3}=5t-3s[/tex]
[tex](7+5c)\cdot2=7\cdot2+5c\cdot2=10c+14[/tex]
[tex](-4)\cdot(5p+3d)=(-4)\cdot5p-4\cdot3d=-20p-12d\\[/tex]