Solve 390=5*30+30(34-1)/2d

$$390 = 5 \times 30 + \frac { 30 ( 34 - 1 ) } { 2 } d$$

Solve for d

$$d=\frac{16}{33}\approx 0.484848485$$

Steps for Solving Linear Equation

Multiply both sides of the equation by 2.

$$780=10\times 30+30\left(34-1\right)d$$

Multiply 10 and 30 to get 300.

$$780=300+30\left(34-1\right)d$$

Subtract 1 from 34 to get 33.

$$780=300+30\times 33d$$

Multiply 30 and 33 to get 990.

$$780=300+990d$$

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

$$300+990d=780$$

Subtract 300 from both sides.

$$990d=780-300$$

Subtract 300 from 780 to get 480.

$$990d=480$$

Divide both sides by 990.

$$d=\frac{480}{990}$$

Reduce the fraction \frac{480}{990} to lowest terms by extracting and canceling out 30.

$$d=\frac{16}{33}$$