a + 2 x b + 3 x c = 19 <span><span><span><span>a +<span> 2 x b </span></span>+<span> 3 x c</span></span> +<span> −2 x b</span></span> =<span> 19 +<span> −<span>2 x b</span></span></span></span> <span><span>a +<span> 3 x c</span></span> =<span><span> −<span>2 x b</span></span> + 19</span></span> <span><span><span>a +<span> 3 x c</span></span> +<span> −<span>3 x c </span></span></span>=<span><span><span> −<span>2 x b </span></span>+ 19 </span>+ <span>−<span>3 x c
</span></span></span></span><span>a =<span><span><span> −<span> 2 x b</span></span> − <span>3 x c</span></span> +<span> 19
</span></span></span>Just continue like this now you just have to plug them in and then solve for each one until you get a solid answer for one variable and then plug them in to find the rest.