Equivalent Equations and Simplification

Which of the following equations is equivalent to:

$$2x+3x+7=10$$

Which equation is equivalent to:

$$3\left(x+5\right)=19$$

Which equation is equivalent to:

$$2a+b=14$$

Which equation is equivalent to:

$$3\left(a+5\right)+7a=10$$

Which equation is equivalent to:

$$\frac{a+b}{3}=7$$

Which equation is equivalent to:

$$4a+7=-a+10$$

Which equation is equivalent to:

$$3a+4b=18$$

Solve for $$m$$ in the equation below.

$$C=10h+21m$$

Find the value of $$\ C$$ if $$h=7$$ and $$m=11.5$$

$$C=10h+21m$$

Find the value of $$\ h$$ if $$C=135.5$$ and $$m=3$$

$$C=10h+21m$$