Make a the subject of the formula:
10a + 9b = 3c

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m∠a is 90°

m∠b is 40°

dilation scale factor 2: starting with δabc, draw the dilation image of the triangle with a center at the origin and a scale factor of two. notice that every coordinate of the original triangle has been multiplied by the scale factor (x2). dilation with scale factor 2, multiply by 2.