Help #4 ​

The trick here, NSS....is just to simplify the numerator first and then the denominator......so we have

2/5t  - 3/3t  =

2/5t  -  1/t          multiply the second fraction by  5 on top/bottom

2/5t - 5/5t   =   (2 - 5 )  / 5t   =   -3 / (5t)

The denominator becomes

1/2t  +  1/2t  =   2/2t  =  1/ (t)

So  we have

(-3/5)t  ÷ 1/t        flip the second fraction and multiply

-3 / (5t)  *  (t)/ 1  =    -3t / 5t   =   -3/5

Do you see how to do this??

Second one :

1/ 20   =  1/r₁  - 1/75       subtract  1/75  from  both sides

(1/20) - (1/75)  =  1/r₁

The common denominator  on the left is 300

15/300  - 4/300  =  1/r₁

(11/300)    =  1/r₁

To find r₁, just flip both fractions over

300/ 11  =  r₁/1

300/11  =  r₁ ≈  27 ohms