Gregg’s phone plan charges $.50 per text message plus $.70 a day. Howard’s plan charges $.30 a text plus $2.50 a day. For what number of texts, a day are the cost of the phone plans the same? Show work.

x=9

Step-by-step explanation:

.5x+.7 = .3x+2.5

     -.7   -.3x

.2x=1.8

/.2    /.2

x=9

.5(9)+.7=5.2

.3(9)+2.5=5.2

for this case we have by definition, if two lines are perpendicular, then the product of their slopes is -1.

then, given the following line:

so,

we are looking for m_ {2}:

then, the line is given by:

we find "b" replacing the given point:

finally, the equation is:

option c