A = BH/2 --- Equation for triangle area
54.52cm² = B(11.6cm)/2 --- Substitute the numbers in for Area and Height
*2 *2 --- Multiply both sides by 2
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109.04cm² = (11.6cm)B
/11.6cm /11.6 cm --- Divide both sides by 11.6cm to isolate B
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9.4cm = B ---Length is equal to 9.4 cm.