Problem background in Illustrator

Trigonometry Problem background.

Open problem.ai

Select the rectangular building. Fill it with the swatch smoke and no stroke.

Create a new swatch called lawn green. C=50,M=0,Y=100,K=0
Color the lawn with it. No stroke.

Create a blue and purple gradient background.
Use it for the background and the windows.
Select the gradient palette. Show options. Drag the purple swatch to the left stop and the blue swatch to the right stop. Drag the gradient to the swatch palette.

Color triangle top building.
Select Texture, Basic Graphics, Basic Graphics_Textures Bird Feet swatch from the swatch library.
Select the building to the far right.
In the appearance palette create a new fill.
Select the top fill with bird feet. Scale it to 200% in pattern. Select the fill, select the scale tool, select patterns and uncheck object.
Select the bottom fill - sunshine.

Color windowed building

Select the rectangle tool. Select twilight blue, no stroke. Click on the artboard. In dialogue box, select 125 pt width and 8 pt height.
With the rectangle still selected, double click on the selection tool.
In the dialogue box byt horizontal 0, vertical -8, distance 0, angle 0, check Ojects and Patterns, click copy.
Drag the new rectangle under the old. Select both rectangles and drag to swatches palette.
Select the windowed building.
Select the new swatch.

Clouds
Select the left cloud. Select the Chalk Scribble Brush.
Select Smoke from the fill palette.
Select 75% Opacity.
Select the graphics style palette - press new graphic style, name it clouds.
Select the right cloud.
Select the new graphic style.

Select the lens flare and use it to your liking.

Select the text problem and fill it with a gradient.