Let J be the money that James saved and let S be the money of his sister.
We have that JAmes saved half the money that his sister saved, then:
![J=(1)/(2)S](https://img.qammunity.org/2023/formulas/mathematics/college/a9lu2w6mcuffuw20vsvtmulomp62cn039f.png)
then if they both save $30, then james will have saved 3/4 as much as his sister. To represent this in the equation, we have to add 30 to the previous eqution (since James saved $30):
![J=(1)/(2)S+30](https://img.qammunity.org/2023/formulas/mathematics/college/51o9tyk44lc47aa6gxq8xij3x4j62aj2c9.png)
But with the $30 more, James will have 3/4 as much as his sister:
![J=(3)/(4)(S+30)](https://img.qammunity.org/2023/formulas/mathematics/college/koscabro0jerhgnosk4b0fz0q31j90mj8t.png)
Now, if we match both equations we get:
![(1)/(2)S+30=(3)/(4)(S+30)](https://img.qammunity.org/2023/formulas/mathematics/college/8n91e9qst9pyqidt5rizw8u4txatoatect.png)