made exercise subtracting fractions nicer so it keeps the pies you we…

…nt through re #267

exercises/subtracting_fractions_with_common_denominators.html

@@ -14,7 +14,10 @@
 
 	<div class="problems">
 		<div>
-			<p class="question"><code><var>fraction( N1, D )</var> - <var>fraction( N2, D )</var> = ?</code></p>
+			<div class="question">
+				<p><code><var>fraction( N1, D )</var> - <var>fraction( N2, D )</var> = ?</code></p>
+				 (simplify your answer)
+			</div>
 			<div class="solution" data-type="improper"><var>( N1 - N2 ) / D</var></div>
 		</div>
 	</div>
@@ -25,25 +28,25 @@
 				PIECH = piechart( [ N1, D - 1 ], ["#e00", "#999"], 2 );
 			</div>
 		<div>
-			<span class="graphie" data-update="pie">
-				PIECH.remove();
-				PIECH =  piechart( [ N1-N2,N2, D - 1 ], ["#e00","#122", "#999"], 2 );
-			</span>
+			<div class="graphie">
+				init({ range: [ [-3, 3], [-3, 3] ], scale: 25 });
+				piechart( [ N1-N2,N2, D - 1 ], ["#e00","#122", "#999"], 2 );
+			</div>
 			<p>Subtract the numerators.</p>
 		</div>
 		<div>
-			<span class="graphie" data-update="pie">
-				PIECH.remove();
-				PIECH =  piechart( [ N1 - N2, D - 1 ], ["#e00", "#999"], 2 );
-			</span>
+			<div class="graphie">
+				init({ range: [ [-3, 3], [-3, 3] ], scale: 25 });
+				piechart( [ N1 - N2, D - 1 ], ["#e00", "#999"], 2 );
+			</div>
 			<p><code><var>fraction( N1, D )</var> - <var>fraction( N2, D )</var> = <var>fraction( N1 - N2, D )</var></code></p>
 		</div>
 		<div data-if="getGCD( N1 - N2, D ) !== 1">
 			<p>Simplify.</p>
-			<span class="graphie" data-update="pie">
-				PIECH.remove();
-				PIECH =  piechart( [ reduce(N1 - N2 , D)[0] , reduce(N1 - N2, D)[1] - 1 ], ["#e00", "#999"], 2 );
-			</span>
+			<div class="graphie">
+				init({ range: [ [-3, 3], [-3, 3] ], scale: 25 });
+				piechart( [ reduce(N1 - N2 , D)[0] , reduce(N1 - N2, D)[1] - 1 ], ["#e00", "#999"], 2 );
+			</div>
 			<p><code><var>fraction( N1 - N2, D )</var> = <var>fractionReduce( N1 - N2, D )</var></code></p>
 		</div>
 	</div>