Lucia finds that (3x²+3x+5)+(7x²-9x+8)=10x²-12x+13. what error did lucia make?

a)she found the difference instead of the sum.
b)she combined the terms 3x² and 7x² incorrectly.
c)she combined the terms 3x and –9x incorrectly.
d)she did not combine all like terms.

Ascientist has 50 grams of a radioactive element. the amount of radioactive element remaining after t days can be determined using the equation (1) after two days the scientist receives a second shipment of 50 grams of the same element. the equation used to represent the amount of shipment 2 remaining after t days is 10) - 50 which of the following is an equivalent form of the expression for the amount remaining in shipment 2? what’s the answer?