Answer:
6)
[tex]5+3(y-4)=5(y+2)-y\\\\5+3y-12=5y+10-y\\\\-7+3y=4y+10\\\\y=-17[/tex]
The error was made by combining the 5+3(y-4) without first distributing the 3 to both the y and -4.
7)
a)
[tex]A(t)=0.30t+45\\B(t)=0.25t+60[/tex]
b) Now we can set each equal to 150 and solve for t
[tex]150=0.30t+45\\\\0.30t=105\\\\t=\frac{105}{0.30} \\\\t=350[/tex]
Rob can send 350 texts per month with plan A
[tex]150=0.25t+60\\\\0.25t=90\\\\t=\frac{90}{0.25} \\\\t=360[/tex]
Rob can send 360 texts per month with plan B
c)
[tex]A(100)=0.30(100)+45\\\\A(100)=30+45\\\\A(100)=75[/tex]
[tex]B(100)=0.25(100)+60\\\\B(100)=25+60\\\\B(100)=85[/tex]
If Rob were to send 100 text messages a month, Plan A would be cheaper
