Present Height plus decreased height equal to original height.
\The equation represents the situation is, .
Apply subtraction property of equality: if , then
.
(Subtract 450 from each side)
(Apply commutative property of addition:
)
(Apply Additive inverse property:
)
(Apply additive identity property:
)
(Subtract:
)
Check:
\To check the solution, substitute in original equation.
(Add:
)
Compare the values, the equation is true. The solution is .
Decrease in the height of the pyramid is 31 ft.