4. In one semester, Doug and Laura spent a combined 230 hours in the tutoring lab. If Doug spent 10 hours less than twice the hours Laura did, how many hours did Doug spend in
the lab?

80 hours

Step-by-step explanation:

let d represent doug, let l represent laura

first, set up a system of equations representing the problem:

since doug spent 10 less than twice the hours laura did, and we know that the total amount of hours they spent together is 230:

l=2d+10

d+l=230

then solve:

*first i rearranged the equations so i can solve this system of equations using elimination method*

l-2d=10

l+d=230

*subtract*

3d=240

d=80

so, doug spent 80 hours in the lab

yes because there is exactly one y value for every x value

for function there can't be more than one value for every x value

32/80  

91/140

the last one 54 doesn't go into 45. 54/100 ?

step-by-step explanation: