If 2x+y=5, then y=5-2x, so she substituted correctly.
x+4x=5x, so she combined like terms correctly.
She didn't subtract 10 from both sides, she added 10 to both sides.
Check the solution:
The answer is: She made no mistake.
x+4x=5x, so she combined like terms correctly.
She didn't subtract 10 from both sides, she added 10 to both sides.
Check the solution:
The answer is: She made no mistake.