### 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: (0 in, 12 in) Current Angle: 0 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

Perform a - b
Problem Statement:
Look on the grid, given a - b. Modify the first Drive-Forward block to move the robot forward by a units. Then modify the Drive-Backward block to move the robot backward by b units. Use the robot's final position to answer the question: "what's a - b?". Refresh to try another problem. Look at Hint and/or Solution for example
```/* Code generated by RoboBlockly v2.0 */
/* Problem Statement:
Add two numbers a - b on a number line. Move the robot tick
mark along the number line, first to the red line, and then
to the green line with the two preplaced driveDistance
blocks. Refresh to try another problem.*/
#include <chplot.h>

CPlot plot;

// Sample Perform 9 - 3
plot.noStrokeColor();
plot.fillColor("#009900");
plot.rectangle(0, 22, 12, 2);
plot.strokeWidth(3);
plot.text("Perform 9 - 3", PLOT_TEXT_LEFT, 1, 22);
robot.traceColor("red", 4);
robot.traceColor("blue", 4);