Rate of change of Resistors

[Aka]

Hi, can someone help me with this question?

 

Three resistors, R1, R2 and R3, are connected in parallel in an electrical circuit. The total resistance, R, in ohms is given by:

 

1/R = 1/R1 + 1/R2 + 1/ R3

 

R, R2, and R3 are increasing at rates of 0.1, 0.5 and 0.7 ohms/s, respectively. Determine the rate at which R1 is changing when R = 50 ohms, R2 = 70 ohms, and R3 = 60 ohms.

 

Find R1

1/50 = 1/R1 + 1/70 + 1/ 60

(1/50)-(1/70)-(1/60)=1/R1

 

How do you solve something that is in the deominator?

 

the i just Plug eerything in to the equation

 

d/dt 1/R = d/dt 1/R1 + d/dt 1/R2 + d/dt 1/ R3

 

right?