This graph shows temperature versus time for some chemical substance as heat is added at a constant rate.

during interval xy, the substance experiences

As a whole the temperature of the chemical substance increases with time. But at the interval x to y the temperature did not change or it remains constant.

arrange the equations with like terms in columns.

analyze the coefficients of x or y.

add the equations and solve for the remaining variable.

substitute the value into either equation and solve.

check the solution.

step-by-step explanation: