$$R _ { i } = \frac { R _ { 1 } + R _ { 2 } } { R _ { 1 } + R _ { 2 } }$$

$$R _ { i } = \frac { R _ { 1 } + R _ { 2 } } { R _ { 1 } + R _ { 2 } }$$
The formula for the total resistance of a circuit is $R _ { t } = \frac { R _ { 1 } R _ { ? } } { R _ { 1 } + R _ { 2 } }$ . If $R _ { t } = 8 \mathrm {~K}$ , and $R _ { 2 } = 10 \mathrm {~K}$ , solve the equation for $R _ { 1 }$ .