Jinxing Primary School donated money to the earthquake-stricken area in Ya'an. The ratio of the amount of money donated by the fourth and fifth grades is 3:4, and the fifth grade donated 1,800 yuan. How much is the total donation for the two grades?
金星小学为雅安地震灾区捐款，四、五年级捐款钱数的比是3：4，五年级捐款1800元，两个年级一共捐款多少元？
<gadget id="calculator">1_800 / 4</gadget>
<output>450</output>

<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<gadget id="calculator">450 * 7</gadget>
<output>3_150</output>

<result>3_150</result>