800 grams of 15% saline solution are prepared from 10% and 20% saline solutions, how many grams are needed for each of these two concentrations? (Pick up the idea: find out the quantitative relationship and use the equation method to solve it)
用浓度为10%和20%的盐水溶液配制成浓度为15%的盐水溶液800克，这两种浓度的溶液各需多少克？(思路点拔：找出数量关系，用方程法求解)
<gadget id="calculator">160 - 120</gadget>
<output>40</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/5) - (1/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">40 / (1/10)</gadget>
<output>400</output>

<gadget id="calculator">800 - 400</gadget>
<output>400</output>

<result>400</result>