A substance experiences rapid changes in temperature over the course of an experiment to test its electrical conductivity. At the start of the experiment the substance is measured to be 70°C, and by the end of the experiment its temperature is measured as −60°C.

130

Step-by-step explanation:

when u you have to subtract you do keep, change, change so it would 70 + 60 instead of 70 - (-60)

it's equivalent, so we can say that its equal.

let's call the denominator x and the numerador is 18 less then denominator, x - 18.

multiply

2.x = 5.(x - 18)

2x = 5x - 90

90 = 5x - 2x

90 = 3x

x = 90/3

x = 30

so:

i’m kinda new to precal but your answer should be 21. hope i got it right.

step-by-step explanation: