Solve & Substitute Test Prep AK

1. A

$$\eqalign{6y&=78\\\div 6&\;\;\div6\\y&=13\\\\6x+3y&=9\\6x+3(13)&=9\\6x+39&=9\\-39&\;\;-39\\6x&=-30\\\div 6&\;\;\div6\\x&=-5\\2x&=-10}$$

2. A

$$\eqalign{\dfrac{5}{6}x&=60\\\div \dfrac{5}{6}&\;\;\div\dfrac{5}{6}\\x&=72\\\\\dfrac{1}{4}(72)&=18}$$

3. A

$$\eqalign{x-2y&=12\\4-2y&=12\\-4\quad&\;\;-4\\-2y&=8\\\div -2&\;\; \div -2\\y&=-4\\\\3y-7&=?\\3(-4)-7&=?\\-12-7&=-19}$$

4. 4

$$\eqalign{9(x-4)&=36\\9x-36&=36\\+36&\;\;+36\\9x&=72\\\div9&\;\;\div 9\\x&=8\\\\x-4=?\\8-4&=4}$$