On a beach trip, Lucy rents a bike from “Wheels by the Waves”, where they rent bikes for $12 plus $3 per hour. If Lucy spent $30, how many hours did she rent a bike?

6 hours

Step-by-step explanation: If you write an equation for this scenario it would be y = 12+3x. 12 is the starting value and x represents how many hours the bike is rented, therefore 3 dollars would be added to the initial 12 each hour. So if Lucy spent $30 then it would change to 30= 12+3x. Now you essentially just need to work backwards. Rearrange the equation and move 12 to the left of the equal sign to make 30-12=3x. Combine vairable to make 18=3x. Divide 3x by 3 to isolate x and divide 18 by 3 as well to make it even. This looks like 18/3=3x/3. Meaning it would end up as 6=x.

the value of v.w= -12.

step-by-step explanation:

we are given three vector r,v and w as:

r = < 5, -5, -2> ; v = < 2, -8, -8> ; w = < -2, 6, -5>

we know that r,v and w could also be represented as:

r=5i-5j-2k

v=2i-8j-8k

and w= -2i+6j-5k

where i,j and k are the unit vectors of x,y and z-axis respectively.

also we know that it has the following property:

i.i=1 ; j.j=1; k.k=1

and i.=j.i=i.k=k.i=j.k=k.j=0

i.e. when we multiply two vectors or we find it's dot product we need to only multiply the components of x coordinates with each other; y with each other and z with each other.

hence, v.w= (2i-8j- -2i+6j-5k)

                  = 2×(-2)+(-8)×(6)+(-8)×(-5)

                  = -4-48+40

                  = -12

hence, v.w= -12