Each week Carina puts 20 more seashells in a jar than she did the week before. If there are 50 seashells in the jar this week, how many will there be in a month?
In one week there will be 50+20=
<gadget id="calculator">50+20</gadget>
<output>70</output>
70 seashells.
In two weeks there will be 70+20=
<gadget id="calculator">70+20</gadget>
<output>90</output>
90 seashells.
In three weeks there will be 90+20=
<gadget id="calculator">90+20</gadget>
<output>110</output>
110 seashells.
In four weeks there will be 110+20=
<gadget id="calculator">110+20</gadget>
<output>130</output>
130 seashells.

<result>130</result>