Solve left(5+5+left(30-1right)dright)30/2=390

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

Solve for d

$$d=\frac{16}{29}\approx 0.551724138$$

Steps for Solving Linear Equation

Multiply both sides by 2.

$$\left(5+5+\left(30-1\right)d\right)\times 30=390\times 2$$

Add 5 and 5 to get 10.

$$\left(10+\left(30-1\right)d\right)\times 30=390\times 2$$

Subtract 1 from 30 to get 29.

$$\left(10+29d\right)\times 30=390\times 2$$

Use the distributive property to multiply 10+29d by 30.

$$300+870d=390\times 2$$

Multiply 390 and 2 to get 780.

$$300+870d=780$$

Subtract 300 from both sides.

$$870d=780-300$$

Subtract 300 from 780 to get 480.

$$870d=480$$

Divide both sides by 870.

$$d=\frac{480}{870}$$

Reduce the fraction \frac{480}{870} to lowest terms by extracting and canceling out 30.

$$d=\frac{16}{29}$$