Solve 30=R*[1+39310^-3(0-20)]

$$30 = R \cdot [ 1 + 393 10 ^ { - 3 } ( 0 - 20 ) ]$$

Solve for R

$$R = -\frac{1500}{343} = -4\frac{128}{343} \approx -4.373177843$$

Steps for Solving Linear Equation

Calculate 10 to the power of -3 and get \frac{1}{1000}.

$$30=R\left(1+393\times \frac{1}{1000}\left(0-20\right)\right)$$

Multiply 393 and \frac{1}{1000} to get \frac{393}{1000}.

$$30=R\left(1+\frac{393}{1000}\left(0-20\right)\right)$$

Subtract 20 from 0 to get -20.

$$30=R\left(1+\frac{393}{1000}\left(-20\right)\right)$$

Multiply \frac{393}{1000} and -20 to get -\frac{393}{50}.

$$30=R\left(1-\frac{393}{50}\right)$$

Subtract \frac{393}{50} from 1 to get -\frac{343}{50}.

$$30=R\left(-\frac{343}{50}\right)$$

Swap sides so that all variable terms are on the left hand side.

$$R\left(-\frac{343}{50}\right)=30$$

Multiply both sides by -\frac{50}{343}, the reciprocal of -\frac{343}{50}.

$$R=30\left(-\frac{50}{343}\right)$$

Multiply 30 and -\frac{50}{343} to get -\frac{1500}{343}.

$$R=-\frac{1500}{343}$$