### Learning Math and Coding with Robots

 Grid: Tics Lines: Width px Hash Lines: Width px Labels: Font px Trace Lines: Robot 1: Width px Robot 2: Width px Robot 3: Width px Robot 4: Width px
 Axes: x-axis y-axis Show Grid Grid: 24x24 inches 36x36 inches 72x72 inches 96x96 inches 192x192 inches Quad: 4 quadrants 1 quadrant Hardware Units: US Customary Metric
 Background:

#### Robot 1

 Initial Position: ( in, in) Initial Angle: deg Current Position: (26 in, 29 in) Current Angle: 225 deg Wheel Radius: 1.75 in1.625 in2.0 in Track Width: in

#### Robot 2

 Initial Position: ( in, in) Initial Angle: deg Current Position: (0 in, 6 in) Current Angle: 0 deg Wheel Radius: 1.75 in1.625 in2.0 in Track Width: in

#### Robot 3

 Initial Position: ( in, in) Initial Angle: deg Current Position: (0 in, 12 in) Current Angle: 0 deg Wheel Radius: 1.75 in1.625 in2.0 in Track Width: in

#### Robot 4

 Initial Position: ( in, in) Initial Angle: deg Current Position: (0 in, 18 in) Current Angle: 0 deg Wheel Radius: 1.75 in1.625 in2.0 in Track Width: in

Delivering Presents
Problem Statement:
The elves accidentally left off some houses on Santa's list. The list is given on the grid. Solve for the missing house number. Then, run the code to answer the prompt question and help Santa deliver the present to that missing house. Refresh for more problems
```/* Code generated by RoboBlockly v2.0 */
#include <chplot.h>
double house_number;
CPlot plot;
double trackwidth = 3.69;

// Describe this function...
void present() {
plot.fillColor("red");
plot.strokeWidth(3);
plot.strokeColor("#c0c0c0");
plot.rectangle(house_number - 1, 2, 3, 3);
plot.quad(house_number - 1, 5, house_number + 2, 5, house_number + 3, 6, house_number, 6);
plot.quad(house_number + 2, 2, house_number + 2, 5, house_number + 3, 6, house_number + 3, 3);
plot.strokeColor("white");
plot.line(house_number + 0.5, 2, house_number + 0.5, 5);
plot.line(house_number + 2.5, 2.5, house_number + 2.5, 5.5);
plot.line(house_number + 0.5, 5, house_number + 1, 5.5);
plot.noFill();
plot.ellipse(house_number, 6, 2, 1, -30);
plot.ellipse(house_number + 2, 6, 2, 1, -150);
plot.strokeWidth(1);
plot.point(house_number + 1, 5.5);
}

printf("Which house is missing its present?"+"\n");
scanf("%lf", &house_number);
robot.traceOff();
plot.strokeWidth(3);
plot.strokeColor("red");
plot.text("21", PLOT_TEXT_LEFT, 10, 33);