Database schema:

CREATE TABLE "Method" (
	"Id" INTEGER NOT NULL -- example: ['2', '1'],
	"Name" TEXT -- example: ['HtmlSharp.HtmlParser.Feed', 'HtmlSharp.HtmlParser.ParseDoctypeElement'],
	"FullComment" TEXT -- example: ['Feeds data into the parser', ' interneral -- scan past <!ELEMENT declarations'],
	"Summary" TEXT -- example: ['Execute the query expression ', 'Converts the query expression into text that corre'],
	"ApiCalls" TEXT -- example: ['System.String.IsNullOrEmpty HtmlSharp.HtmlParser.G', 'HtmlSharp.HtmlParser.ScanName System.Collections.G'],
	"CommentIsXml" INTEGER -- example: ['0', '1'],
	"SampledAt" INTEGER -- example: ['636430963695709898', '636430963695654788'],
	"SolutionId" INTEGER -- example: ['2', '1'],
	"Lang" TEXT -- example: ['fr', 'en'],
	"NameTokenized" TEXT -- example: ['html parser parse doctype element', 'html parser feed'],
	PRIMARY KEY ("Id")
)


CREATE TABLE "MethodParameter" (
	"Id" INTEGER NOT NULL -- example: ['2', '1'],
	"MethodId" TEXT -- example: ['2', '1'],
	"Type" TEXT -- example: ['System.Int32', 'System.String'],
	"Name" TEXT -- example: ['data', 'i'],
	PRIMARY KEY ("Id")
)


CREATE TABLE "Repo" (
	"Id" INTEGER NOT NULL -- example: ['2', '1'],
	"Url" TEXT -- example: ['https://github.com/unclebob/nslim.git', 'https://github.com/wallerdev/htmlsharp.git'],
	"Stars" INTEGER -- example: ['14', '6'],
	"Forks" INTEGER -- example: ['2', '3'],
	"Watchers" INTEGER -- example: ['14', '6'],
	"ProcessedTime" INTEGER -- example: ['636430963247108053', '636472436323838240'],
	PRIMARY KEY ("Id")
)


CREATE TABLE "Solution" (
	"Id" INTEGER NOT NULL -- example: ['2', '1'],
	"RepoId" INTEGER -- example: ['1', '3'],
	"Path" TEXT -- example: ['wallerdev_htmlsharp\\HtmlSharp.sln', 'maravillas_linq-to-delicious\\tasty.sln'],
	"ProcessedTime" INTEGER -- example: ['636430963721734366', '636430963695642191'],
	"WasCompiled" INTEGER -- example: ['0', '1'],
	PRIMARY KEY ("Id")
)

Question: How many percent more of the watchers for the repository of solution No.83855 than No.1502?
Evidence: solution No. refers to Solution.Id; percentage = DIVIDE(MULTIPLY(SUBTRACT(SUM(Solution.Id = 83855), SUM(Solution.Id = 1502)), 100)), SUM(Soltution.Id = 1502);

SQL:
SELECT CAST(SUM(CASE WHEN T2.Id = 83855 THEN T1.Watchers ELSE 0 END) - SUM(CASE WHEN T2.Id = 1502 THEN T1.Watchers ELSE 0 END) AS REAL) * 100 / SUM(CASE WHEN T2.Id = 1502 THEN T1.Watchers ELSE 0 END) FROM Repo AS T1 INNER JOIN Solution AS T2 ON T1.Id = T2.RepoId