Which sentence does not belong with the other 3?
a.) x + 12 = 12 + x
b.) 7h = h ∙ 7
c.)1 + a = a + 1
d.) n ÷ 2 = 2 ÷ n

Before simplifying, how many terms are there in the expression 2x - 5y + 3 + x?

Aline has a slope of and a y-intercept of –2. what is the x-intercept of the line?

Aspacecraft can attain a stable orbit 300 kilometers above earth if it reaches a velocity of 7.7 kilometers per second. the formula for a rocket's maximum velocity v in kilometers per second is vequalsminus0.0098tplusc ln upper r, where t is the firing time in seconds, c is the velocity of the exhaust in kilometers per second, and r is the ratio of the mass of the rocket filled with fuel to the mass of the rocket without fuel. find the velocity of a spacecraft whose booster rocket has a mass ratio of 20, an exhaust velocity of 2.1 km/s, and a firing time of 15 s. can the spacecraft achieve a stable orbit 300 km above earth?