Question 932491
<pre>
{{{system(a[6]=a[5]+d,a[7]=a[6]+d)}}}

{{{system(a[6]=46+d,60=a[6]+d)}}}

Use substitution of 46+d for a<sub>6</sub> in 2nd equation

{{{60=46+d+d}}}
{{{60=46+2d}}}
{{{14=2d}}}
{{{7=d}}}

Then use formula

{{{a[n]=a[1]+(n-1)d}}} with n=5 and a<sub>5</sub>=46

{{{a[5]=a[1]+(5-1)7}}}

{{{46=a[1]+(4)7}}}
{{{46=a[1]+28}}}
{{{18=a[1]}}}

So 

{{{a[n]=a[1]+(n-1)d}}} becomes:

{{{a[n]=18+(n-1)7}}}

{{{a[n]=18+7(n-1)}}}

{{{a[n]=18+7n-7}}}

{{{a[n]=7n+11}}}

You didn't say what you wanted to find but you can use
that formula to find any term.

Or you ccan find a formula to use for the sum of any
numer of terms:

{{{S[n]=expr(n/2)(2a[1]+(n-1)d)}}}

{{{S[n]=expr(n/2)(2(18)+(n-1)7)}}}

{{{S[n]=expr(n/2)(36^""+7(n-1))}}}

{{{S[n]=expr(n/2)(36+7n-7)}}}

{{{S[n]=expr(n/2)(7n+29)}}}

Edwin</pre>